Recent advances in two-dimensional layered systems have greatly enriched electronic transport studies, particularly in inter-layer Coulomb drag research. Here, systematic transport measurements were conducted in graph...Recent advances in two-dimensional layered systems have greatly enriched electronic transport studies, particularly in inter-layer Coulomb drag research. Here, systematic transport measurements were conducted in graphene-based electronic double-layer structures, revealing giant yet reproducible drag fluctuations at cryogenic temperatures. These fluctuations' characteristics, including amplitude and peak/valley spacing, are mainly determined by the drag layer's carrier dynamics rather than the drive layer's, resulting in violation of the Onsager reciprocity relation. Notably, the drag fluctuations remain observable up to 35 K, far exceeding universal conductance fluctuations within individual layers. This suggests enhanced phase coherence in inter-layer drag compared to single-layer transport, as further confirmed by quantitative analysis of auto-correlation fields of fluctuations under magnetic fields. Our findings provide new insights into quantum interference effects and their interplay with Coulomb interactions in solids. The observations of significant drag fluctuations could potentially help address chaotic signals between nearby components in nanoscale devices.展开更多
Inspired by the aquatic-adapted pit structures of the Cybister beetles that enable high-speed swimming,this study employs warp-knitted technology to fabricate drag-reduction swimwear textiles.Eight distinct fabric mor...Inspired by the aquatic-adapted pit structures of the Cybister beetles that enable high-speed swimming,this study employs warp-knitted technology to fabricate drag-reduction swimwear textiles.Eight distinct fabric morphologies were produced,and a self-developed high-precision dynamic drag measurement device was used to systematically analyze the mechanisms underlying the drag-reduction performance of these biomimetic pit structures.The device incorporates a servomotor,ball screw linkage,and high-precision tension sensor,enabling real-time and accurate detection of fluid drag forces.It effectively overcomes the limitations of traditional indirect measurement methods,including dynamic response lag and insufficient accuracy.Experimental results demonstrate that the hydrophobic small-pit fabric(4^(#))achieves an 84% drag reduction at 400 mm/s,outperforming the control sample(warp-knitted fabric 7^(#)).This significant reduction is attributed to the Cassie state established on the hydrophobic surface,which substantially decreases viscous drag and the microvortices generated by the pit structures,which delay flow separation and effectively minimize pressure drag.Furthermore,small-pit fabrics demonstrate a drag reduction rate 26% to 50% higher than that of large-pit structures,highlighting the critical importance of matching the pit scale to the thickness of the near-wall viscous sublayer for optimal drag reduction.This study establishes a theoretical foundation for the biomimetic design of high-performance drag-reduction swimsuits.The developed drag-measuring device also provides a standardized experimental platform for hydrodynamic studies of flexible materials,supporting a shift from empirical design methodologies to theory-driven approaches in drag-reduction technology and exhibiting significant potential for future advancements.展开更多
The cutaneous ridges on dolphin skin have long been believed to effectively reduce friction drag, thereby contributing to overall drag reduction. However, since these skin ridges are oriented perpendicular to the swim...The cutaneous ridges on dolphin skin have long been believed to effectively reduce friction drag, thereby contributing to overall drag reduction. However, since these skin ridges are oriented perpendicular to the swimming direction, they also generate additional pressure drag, raising questions about the impact of the shape-induced pressure forces on swimming. Inspired by the microvibrations observed on dolphin skin, we hypothesize that the microstructure on dolphin skin is not static but dynamically oscillates in the form of Longitudinal Micro-Ultrasonic Waves (LMUWs). To explore this, we carried out a series of Computational Fluid Dynamics (CFD) simulations based on Large Eddy Simulation (LES) model to investigate the impact of pressure drag on the total drag acting on an oscillating skin surface under realistic turbulent flow conditions. The results indicate that the dynamic skin oscillations induce a new dynamic Stokes boundary layer, which has the potential to convert pressure drag into a negative force, thereby reducing total drag under the influence of traveling LMUW excitations. Furthermore, a relative velocity ξ, defined as the difference between the wave speed c and the external flow speed U, is introduced to evaluate the drag-reduction effect dominated by pressure. The findings reveal that pressure drag remains negative when ξ > 0. As ξ increases, the thrust effect induced by negative pressure becomes increasingly significant, ultimately counteracting friction drag and eliminating total drag. This pressure-dominated drag reduction mechanism thus demonstrates a novel strategy for the drag reduction technology and the potential of unveiling the mysteries behind dolphin swimming.展开更多
Reducing the resistance of vehicles,ships,aircraft and other means of transport during movement can significantly improve the speed,save energy and reduce emissions.After billions of years of continuous evolution,orga...Reducing the resistance of vehicles,ships,aircraft and other means of transport during movement can significantly improve the speed,save energy and reduce emissions.After billions of years of continuous evolution,organisms in nature have gradually developed the ability to move at high speed to achieve better survival.These evolved organisms provide a perfect template for the human development of drag reduction materials.Revealing the unique physiological structural characteristics of organisms and their relationship with resistance during movement can provide a feasible approach tosolving the problem of reducing friction resistance.Whether flying in the sky,running on the ground,swimming in the water,or even living in the soil,many creatures in various environments have the ability to reduce resistance.Driven by these inspirations,researchers have done a lot of work to explore and imitate these biological epidermis structures to achieve drag reduction.In this paper,the biomimetic drag reduction materials is introduced in detail in the order of drag reduction mechanism,structural characteristics of biological epidermis(including marine animals,flying animals,soil animals and plants),biomimetic preparation methods,performance testing methods and application fields.Finally,the potential of various biomimetic drag reduction materials in engineering application and the problems to be overcome are summarized and prospected.This paper can help readers comprehensively understand the research progress of biomimetic drag reduction materials,and provide reference for further designing the next generation of drag reduction materials.展开更多
Bioinspired superhydrophobic surfaces have been used for drag reduction.However,the secondary structures and the air cushions on these surfaces could be destructed in a flow,losing the effect of drag reduction.Here,a ...Bioinspired superhydrophobic surfaces have been used for drag reduction.However,the secondary structures and the air cushions on these surfaces could be destructed in a flow,losing the effect of drag reduction.Here,a stainless-steel surface with mushroom-like cross-section(SMC)and diamond cavities(SMCD)having a drag reduction rate up to 19.37%is developed by 3D printing.The concealed re-entrant structures in SMCD prevent the infiltration of water into the chamber and form gas cushions,which converts the sliding friction at liquid-solid interface into rolling friction at liquid-gas interface,realizing the drag reduction.Meanwhile,98.3%of air can be maintained in the chamber in a flow with Reynolds number(Re)of 9×10^(5),ensuring the drag reduction in a high-velocity flow.Moreover,the continuous top stainless-steel surface and the supporting mesh network protect the critical re-entrant structures,ensuring the robustness of SMC.With the bioinspired design and one-step additive manufacturing process,SMC holds great potential for large-area production and applications requiring robust drag reduction.展开更多
Ocean surface waves and upper sea circulation are primarily propelled by wind force and are usually expressed in terms of sea surface drag coefficient(c_(d))that increases with sea surface roughness and wind speed.Thi...Ocean surface waves and upper sea circulation are primarily propelled by wind force and are usually expressed in terms of sea surface drag coefficient(c_(d))that increases with sea surface roughness and wind speed.This work discussed the c_(d)parameterization at Aiyetoro,Ilaje Local Government Area,Ondo State,Southwestern Nigeria,to quantify the exchange of momentum in this region,The dependence of cd on some one hourly averaged variables sourced from ERA5 Reanalysis over a 71 year period(1950-2020)was clearly analysed.Results of the monthly mean and variability of cd and u10 over the study area showed that November had the lowest monthly mean cd and u10,with values of 0.000825 and 3.38 m/s,respectively,and August had the highest values of 0.001031 and 5.66 m/s,respectively.Furthermore,the cd variability is lowest(63.24%)in November and highest(106.35%)in August.The variability for u10 is lowest in March(198.18%)and greatest in October(304.37%).For the study location,five parameterizations,were statistically evaluated for the predictive power of c_(d) on an annual,seasonal and monthly basis.Furthermore,the cd showed improved performance when using monthly values than when using annual and seasonal values.The equations yielded better performance in the wet season than in the dry season.展开更多
In this paper,a series of flutter simulations are carried out to investigate the effects of split drag rudder(SDR)on the transonic flutter characteristic of rigid NACA 64A010.A structural dynamic model addressing two-...In this paper,a series of flutter simulations are carried out to investigate the effects of split drag rudder(SDR)on the transonic flutter characteristic of rigid NACA 64A010.A structural dynamic model addressing two-degree-of-freedom pitch-plunge aeroelastic oscillations was coupled with the unsteady Reynolds-averaged Navier-Stokes equations to perform flutter simulation.Meanwhile,the influence mechanism of SDR on flutter boundary is explained through aerodynamic work and the correlated shock wave location.The results show that the SDR delays the shock wave shifting downstream,and the Mach number corresponding to reaching freeze region increases as the split angle increases.Therefore,the peak value of aerodynamic moment coefficient amplitude and the sharp ascent process of phase occurs at higher Mach number,which leads to the delay in the occurrence of the transonic dip.Besides,before the transonic dip of airfoil without SDR occurs,the aerodynamic moment phase of airfoil with the SDR decreases slowly due to the decrease in the speed of shock wave moving downstream.This results in an increased flutter speed when employing the SDR before the transonic dip of airfoil without SDR occurs.Meanwhile,the effects of asymmetric split angles on the transonic flutter characteristics are also investigated.Before the transonic dip of airfoil without SDR occurs,the flutter characteristic is dominated by the smaller split angle.展开更多
The primary objective in aircraft transportation is to minimize turbulent drag, thereby conserving energy and reducing emissions. We propose a sector-shaped counter-flow dielectric barrier discharge plasma actuator, w...The primary objective in aircraft transportation is to minimize turbulent drag, thereby conserving energy and reducing emissions. We propose a sector-shaped counter-flow dielectric barrier discharge plasma actuator, which leverages jet synthesis for drag reduction. A drag control experiment was conducted in a low-speed wind tunnel with a controlled flow velocity of 9.6 m/s(Re = 1.445 × 10^(4)). This study investigated the effects of varying pulse frequencies and actuation voltages on the turbulent boundary layer. Using a hot-wire measurement system, we analyzed the pulsating and time-averaged velocity distributions within the boundary layer to evaluate the streamwise turbulent drag reduction. The results show that the local TDR decreases as the pulse frequency increases, reaching a maximum reduction of approximately 20.97% at a pulse frequency of 50 Hz. In addition, as the actuation voltage increases, the friction coefficient decreases, increasing the drag reduction rate. The maximum drag reduction of approximately 33.34% is achieved at an actuation voltage of 10 kV.展开更多
In multiphase pumps transporting gas-liquid two-phase flows,the high-speed rotation of the impeller induces complex deformations in bubble shapes within the flow domain,making the prediction of gasliquid two-phase dra...In multiphase pumps transporting gas-liquid two-phase flows,the high-speed rotation of the impeller induces complex deformations in bubble shapes within the flow domain,making the prediction of gasliquid two-phase drag forces highly challenging in numerical simulations.To achieve precise prediction of the drag forces on irregular bubbles within multiphase pumps,this study modifies the existing bubble drag force model and applies the revised model to the prediction of gas-liquid two-phase flow within multiphase pumps.The research findings indicate that the modified drag force model significantly enhances the accuracy of predicting flow characteristics within the pump,particularly under high gas volume fraction conditions.The simulation results for gas phase distribution and vorticity exhibit strong agreement with experimental data.The modified drag model better captures the accumulation of the gas phase at the suction side of the impeller outlet.It also accurately predicts the vortex characteristics induced by bubble backflow from the trailing edges of the diffuser.Additionally,the adjustment of the drag coefficient enhances the model’s ability to represent local flow field characteristics,thereby optimizing the performance simulation methods of multiphase pumps.Compared to traditional drag force models,the modified model reduces prediction errors in head and efficiency by 36.4%and 27.5%,respectively.These results provide important theoretical foundations and model support for improving the accuracy of gas-liquid two-phase flow simulations and optimizing the design of multiphase pumps under high gas volume fraction conditions.展开更多
In the preparation of firing tables, the determination of projectile drag coefficientsthrough firing test radar data reduction is very important. Many methods have been developed for this work but none of them appear ...In the preparation of firing tables, the determination of projectile drag coefficientsthrough firing test radar data reduction is very important. Many methods have been developed for this work but none of them appear to be satisfactory in one Way or another. Inthis paper a multi-spline model of drag coefficient (cd) curve is developed that can guaranteefirst derivative continuity of the cd curve and has good flexibility of fitting accurately to acd curve from subsonic up to supersonic range. Practical firing data reduction tests showboth fast convergence and accurate fitting results. Typical velocity fitting RMS errors are0.05-0.08 m/s.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos.12474051 and 92165201)the Chinese Academy of Sciences Project for Young Scientists in Basic Research (Grant No.YSBR-046)+1 种基金the National Key Research and Development Program of China (Grant No.2023YFA1406300)the Anhui Provincial Natural Science Foundation (Grant Nos.2308085J11 and2308085QA14)。
文摘Recent advances in two-dimensional layered systems have greatly enriched electronic transport studies, particularly in inter-layer Coulomb drag research. Here, systematic transport measurements were conducted in graphene-based electronic double-layer structures, revealing giant yet reproducible drag fluctuations at cryogenic temperatures. These fluctuations' characteristics, including amplitude and peak/valley spacing, are mainly determined by the drag layer's carrier dynamics rather than the drive layer's, resulting in violation of the Onsager reciprocity relation. Notably, the drag fluctuations remain observable up to 35 K, far exceeding universal conductance fluctuations within individual layers. This suggests enhanced phase coherence in inter-layer drag compared to single-layer transport, as further confirmed by quantitative analysis of auto-correlation fields of fluctuations under magnetic fields. Our findings provide new insights into quantum interference effects and their interplay with Coulomb interactions in solids. The observations of significant drag fluctuations could potentially help address chaotic signals between nearby components in nanoscale devices.
基金the financial support from the Fundamental Research Funds for the Central Universities(JUSRP122003)the fellowship of China Postdoctoral Science Foundation(2022TQ0123).
文摘Inspired by the aquatic-adapted pit structures of the Cybister beetles that enable high-speed swimming,this study employs warp-knitted technology to fabricate drag-reduction swimwear textiles.Eight distinct fabric morphologies were produced,and a self-developed high-precision dynamic drag measurement device was used to systematically analyze the mechanisms underlying the drag-reduction performance of these biomimetic pit structures.The device incorporates a servomotor,ball screw linkage,and high-precision tension sensor,enabling real-time and accurate detection of fluid drag forces.It effectively overcomes the limitations of traditional indirect measurement methods,including dynamic response lag and insufficient accuracy.Experimental results demonstrate that the hydrophobic small-pit fabric(4^(#))achieves an 84% drag reduction at 400 mm/s,outperforming the control sample(warp-knitted fabric 7^(#)).This significant reduction is attributed to the Cassie state established on the hydrophobic surface,which substantially decreases viscous drag and the microvortices generated by the pit structures,which delay flow separation and effectively minimize pressure drag.Furthermore,small-pit fabrics demonstrate a drag reduction rate 26% to 50% higher than that of large-pit structures,highlighting the critical importance of matching the pit scale to the thickness of the near-wall viscous sublayer for optimal drag reduction.This study establishes a theoretical foundation for the biomimetic design of high-performance drag-reduction swimsuits.The developed drag-measuring device also provides a standardized experimental platform for hydrodynamic studies of flexible materials,supporting a shift from empirical design methodologies to theory-driven approaches in drag-reduction technology and exhibiting significant potential for future advancements.
基金supported by the Japan Society for the Promotion of Science(JSPS KAKENHI No.23H01373).
文摘The cutaneous ridges on dolphin skin have long been believed to effectively reduce friction drag, thereby contributing to overall drag reduction. However, since these skin ridges are oriented perpendicular to the swimming direction, they also generate additional pressure drag, raising questions about the impact of the shape-induced pressure forces on swimming. Inspired by the microvibrations observed on dolphin skin, we hypothesize that the microstructure on dolphin skin is not static but dynamically oscillates in the form of Longitudinal Micro-Ultrasonic Waves (LMUWs). To explore this, we carried out a series of Computational Fluid Dynamics (CFD) simulations based on Large Eddy Simulation (LES) model to investigate the impact of pressure drag on the total drag acting on an oscillating skin surface under realistic turbulent flow conditions. The results indicate that the dynamic skin oscillations induce a new dynamic Stokes boundary layer, which has the potential to convert pressure drag into a negative force, thereby reducing total drag under the influence of traveling LMUW excitations. Furthermore, a relative velocity ξ, defined as the difference between the wave speed c and the external flow speed U, is introduced to evaluate the drag-reduction effect dominated by pressure. The findings reveal that pressure drag remains negative when ξ > 0. As ξ increases, the thrust effect induced by negative pressure becomes increasingly significant, ultimately counteracting friction drag and eliminating total drag. This pressure-dominated drag reduction mechanism thus demonstrates a novel strategy for the drag reduction technology and the potential of unveiling the mysteries behind dolphin swimming.
基金the National Natural Science Foundation of China(No.52305236)supported by National Natural Science Foundation of China.
文摘Reducing the resistance of vehicles,ships,aircraft and other means of transport during movement can significantly improve the speed,save energy and reduce emissions.After billions of years of continuous evolution,organisms in nature have gradually developed the ability to move at high speed to achieve better survival.These evolved organisms provide a perfect template for the human development of drag reduction materials.Revealing the unique physiological structural characteristics of organisms and their relationship with resistance during movement can provide a feasible approach tosolving the problem of reducing friction resistance.Whether flying in the sky,running on the ground,swimming in the water,or even living in the soil,many creatures in various environments have the ability to reduce resistance.Driven by these inspirations,researchers have done a lot of work to explore and imitate these biological epidermis structures to achieve drag reduction.In this paper,the biomimetic drag reduction materials is introduced in detail in the order of drag reduction mechanism,structural characteristics of biological epidermis(including marine animals,flying animals,soil animals and plants),biomimetic preparation methods,performance testing methods and application fields.Finally,the potential of various biomimetic drag reduction materials in engineering application and the problems to be overcome are summarized and prospected.This paper can help readers comprehensively understand the research progress of biomimetic drag reduction materials,and provide reference for further designing the next generation of drag reduction materials.
基金supported by National Natural Science Foundation of China(52373119,52475310)the National Key R&D Program of China(2022YFB4701000).
文摘Bioinspired superhydrophobic surfaces have been used for drag reduction.However,the secondary structures and the air cushions on these surfaces could be destructed in a flow,losing the effect of drag reduction.Here,a stainless-steel surface with mushroom-like cross-section(SMC)and diamond cavities(SMCD)having a drag reduction rate up to 19.37%is developed by 3D printing.The concealed re-entrant structures in SMCD prevent the infiltration of water into the chamber and form gas cushions,which converts the sliding friction at liquid-solid interface into rolling friction at liquid-gas interface,realizing the drag reduction.Meanwhile,98.3%of air can be maintained in the chamber in a flow with Reynolds number(Re)of 9×10^(5),ensuring the drag reduction in a high-velocity flow.Moreover,the continuous top stainless-steel surface and the supporting mesh network protect the critical re-entrant structures,ensuring the robustness of SMC.With the bioinspired design and one-step additive manufacturing process,SMC holds great potential for large-area production and applications requiring robust drag reduction.
基金supported by Department of Engineering,University of Campania Luigi Vanvitelli,81031 Aversa,Italy.
文摘Ocean surface waves and upper sea circulation are primarily propelled by wind force and are usually expressed in terms of sea surface drag coefficient(c_(d))that increases with sea surface roughness and wind speed.This work discussed the c_(d)parameterization at Aiyetoro,Ilaje Local Government Area,Ondo State,Southwestern Nigeria,to quantify the exchange of momentum in this region,The dependence of cd on some one hourly averaged variables sourced from ERA5 Reanalysis over a 71 year period(1950-2020)was clearly analysed.Results of the monthly mean and variability of cd and u10 over the study area showed that November had the lowest monthly mean cd and u10,with values of 0.000825 and 3.38 m/s,respectively,and August had the highest values of 0.001031 and 5.66 m/s,respectively.Furthermore,the cd variability is lowest(63.24%)in November and highest(106.35%)in August.The variability for u10 is lowest in March(198.18%)and greatest in October(304.37%).For the study location,five parameterizations,were statistically evaluated for the predictive power of c_(d) on an annual,seasonal and monthly basis.Furthermore,the cd showed improved performance when using monthly values than when using annual and seasonal values.The equations yielded better performance in the wet season than in the dry season.
文摘In this paper,a series of flutter simulations are carried out to investigate the effects of split drag rudder(SDR)on the transonic flutter characteristic of rigid NACA 64A010.A structural dynamic model addressing two-degree-of-freedom pitch-plunge aeroelastic oscillations was coupled with the unsteady Reynolds-averaged Navier-Stokes equations to perform flutter simulation.Meanwhile,the influence mechanism of SDR on flutter boundary is explained through aerodynamic work and the correlated shock wave location.The results show that the SDR delays the shock wave shifting downstream,and the Mach number corresponding to reaching freeze region increases as the split angle increases.Therefore,the peak value of aerodynamic moment coefficient amplitude and the sharp ascent process of phase occurs at higher Mach number,which leads to the delay in the occurrence of the transonic dip.Besides,before the transonic dip of airfoil without SDR occurs,the aerodynamic moment phase of airfoil with the SDR decreases slowly due to the decrease in the speed of shock wave moving downstream.This results in an increased flutter speed when employing the SDR before the transonic dip of airfoil without SDR occurs.Meanwhile,the effects of asymmetric split angles on the transonic flutter characteristics are also investigated.Before the transonic dip of airfoil without SDR occurs,the flutter characteristic is dominated by the smaller split angle.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 61971345 and 52107174)。
文摘The primary objective in aircraft transportation is to minimize turbulent drag, thereby conserving energy and reducing emissions. We propose a sector-shaped counter-flow dielectric barrier discharge plasma actuator, which leverages jet synthesis for drag reduction. A drag control experiment was conducted in a low-speed wind tunnel with a controlled flow velocity of 9.6 m/s(Re = 1.445 × 10^(4)). This study investigated the effects of varying pulse frequencies and actuation voltages on the turbulent boundary layer. Using a hot-wire measurement system, we analyzed the pulsating and time-averaged velocity distributions within the boundary layer to evaluate the streamwise turbulent drag reduction. The results show that the local TDR decreases as the pulse frequency increases, reaching a maximum reduction of approximately 20.97% at a pulse frequency of 50 Hz. In addition, as the actuation voltage increases, the friction coefficient decreases, increasing the drag reduction rate. The maximum drag reduction of approximately 33.34% is achieved at an actuation voltage of 10 kV.
基金funded by Sichuan Natural Science Foundation Outstanding Youth Science Foundation(No.2024NSFJQ0012)Key project of Regional Innovation and Development Joint Fund of National Natural Science Foundation(No.U23A20669)Sichuan Science and Technology Program(2022ZDZX0041).
文摘In multiphase pumps transporting gas-liquid two-phase flows,the high-speed rotation of the impeller induces complex deformations in bubble shapes within the flow domain,making the prediction of gasliquid two-phase drag forces highly challenging in numerical simulations.To achieve precise prediction of the drag forces on irregular bubbles within multiphase pumps,this study modifies the existing bubble drag force model and applies the revised model to the prediction of gas-liquid two-phase flow within multiphase pumps.The research findings indicate that the modified drag force model significantly enhances the accuracy of predicting flow characteristics within the pump,particularly under high gas volume fraction conditions.The simulation results for gas phase distribution and vorticity exhibit strong agreement with experimental data.The modified drag model better captures the accumulation of the gas phase at the suction side of the impeller outlet.It also accurately predicts the vortex characteristics induced by bubble backflow from the trailing edges of the diffuser.Additionally,the adjustment of the drag coefficient enhances the model’s ability to represent local flow field characteristics,thereby optimizing the performance simulation methods of multiphase pumps.Compared to traditional drag force models,the modified model reduces prediction errors in head and efficiency by 36.4%and 27.5%,respectively.These results provide important theoretical foundations and model support for improving the accuracy of gas-liquid two-phase flow simulations and optimizing the design of multiphase pumps under high gas volume fraction conditions.
文摘In the preparation of firing tables, the determination of projectile drag coefficientsthrough firing test radar data reduction is very important. Many methods have been developed for this work but none of them appear to be satisfactory in one Way or another. Inthis paper a multi-spline model of drag coefficient (cd) curve is developed that can guaranteefirst derivative continuity of the cd curve and has good flexibility of fitting accurately to acd curve from subsonic up to supersonic range. Practical firing data reduction tests showboth fast convergence and accurate fitting results. Typical velocity fitting RMS errors are0.05-0.08 m/s.
