Background and Objective The natural history of type B aortic intramural hematoma(IMH)is highly heterogeneous.A computational fluid dynamics(CFD)model can be utilized to calculate a range of data pertinent to flow dyn...Background and Objective The natural history of type B aortic intramural hematoma(IMH)is highly heterogeneous.A computational fluid dynamics(CFD)model can be utilized to calculate a range of data pertinent to flow dynamics,including flow rates,blood velocity,pressure,and wall shear stress.This study presents a series of CFD simulations that model the dynamic progression from type B aortic IMH to false lumen formation.Methods A 66-year-old male patient presenting with chest and back pain underwent aortic computed tomography angiography(CTA),and a 3D patient-specific model was constructed.To evaluate the hemodynamic environment,the velocity,pressure,time-averaged wall shear stress(TAWSS),and oscillatory shear index(OSI)were calculated.Results A modest quantity of slow flow and recirculation flow was observed in the vicinity of the ulcer-like protrusion(ULP).During the formation of the false lumen,low-velocity blood flow entered the false lumen and resulted in vortex flow.ULPs were located in the region with higher TAWSS,and some high OSIs were found on the ULPs.Conclusion This preliminary study suggests a potential association between the TAWSS or OSI and progression from type B aortic IMH to aortic dissection.展开更多
Fibrous-type flters are used to capture dust particles in mining and other occupations where personnel are exposed for prolonged periods.Dust cleansing devices including fooded-bed dust scrubbers use these mesh-type m...Fibrous-type flters are used to capture dust particles in mining and other occupations where personnel are exposed for prolonged periods.Dust cleansing devices including fooded-bed dust scrubbers use these mesh-type multi-layered flters.These flters trap dust particles efciently on their surface and inside their mesh.However,their continued operation leads to dust build-up and clogging.This results in increased resistance of the flter and lowered airfow rate through the scrubber.This could potentially enhance the exposure of the miners.A non-clogging self-cleaning impingement screen type dust flter was designed by the authors for use in mining and industrial dust cleansing applications.The flter guides dirt-laden air through rapidly turning paths which forces it to shed heavier particles.The particles impact one of the impermeable solid metallic flter surfaces and are removed from the airstream.A full cone water spray installed upstream prevents any surface buildup of dust.This paper summaried the computer models generated to show the flter operations and laboratory experiments including optical particle counting to establish the cleaning efciency.展开更多
The sensitivity of moving particle semi-implicit(MPS)simulations to numerical parameters is investigated in this study.Although the verifcation and validation(V&V)are important to ensure accurate numerical results...The sensitivity of moving particle semi-implicit(MPS)simulations to numerical parameters is investigated in this study.Although the verifcation and validation(V&V)are important to ensure accurate numerical results,the MPS has poor perfor-mance in convergences with a time step size.Therefore,users of the MPS need to tune numerical parameters to ft results into benchmarks.However,such tuning parameters are not always valid for other simulations.We propose a practical numerical condition for the MPS simulation of a two-dimensional wedge slamming problem(i.e.,an MPS-slamming condition).The MPS-slamming condition is represented by an MPS-slamming number,which provides the optimum time step size once the MPS-slamming number,slamming velocity,deadrise angle of the wedge,and particle size are decided.The simulation study shows that the MPS results can be characterized by the proposed MPS-slamming condition,and the use of the same MPS-slamming number provides a similar fow.展开更多
This study investigates the accuracy and efficiency of a convolutional autoencoder in predicting flow solutions of diverse characteristics,including strong local nonlinea rity and unsteady wake vortices.Modifications ...This study investigates the accuracy and efficiency of a convolutional autoencoder in predicting flow solutions of diverse characteristics,including strong local nonlinea rity and unsteady wake vortices.Modifications to the standard U-net method were made suitable for non-Cartesian CFD mesh topology,enhancing solution accuracy.Additionally,conditions for predicting flows in unseen environments are integrated into a bottleneck layer between the encoder and decoder structures,guiding flow interpolation or extrapolation and parameter types.For direct comparison,this study uses a proper orthogonal decomposition(POD)-based ROM with linear reconstruction using dominant basis vectors from the flow solution space.Interpolation and extrapolation of generalized coordinates are performed using Gaussian process regression(GPR)and Long Short-Term Memory(LSTM)networks,respectively.The Conditional Unet(CUnet)'s accuracy is demonstrated through inviscid transonic airfoil flows,capturing shock waves effectively.Additionally,it can also be used for predicting the flow field of the three-dimensional shape of the Onera M6 wing.Vortex shedding flows around an Eppler airfoil at a 16-degree angle of attack in turbulent conditions were well-resolved,with root mean squared errors under 1%compared to full-order CFD results.Remarkably,the CUnet's computational efficiency is highlighted as the wall clock CPU time for these 2D flows was less than one second.Finally,the ROM's effectiveness is further validated through successful multi-point shape optimization,minimizing wave drag of RAE 2822 airfoils across subsonic to transonic conditions.This resulted in a maximum drag reduction of 37.38%at Mach 0.74 without performance degradation at off-design conditions.展开更多
文摘Background and Objective The natural history of type B aortic intramural hematoma(IMH)is highly heterogeneous.A computational fluid dynamics(CFD)model can be utilized to calculate a range of data pertinent to flow dynamics,including flow rates,blood velocity,pressure,and wall shear stress.This study presents a series of CFD simulations that model the dynamic progression from type B aortic IMH to false lumen formation.Methods A 66-year-old male patient presenting with chest and back pain underwent aortic computed tomography angiography(CTA),and a 3D patient-specific model was constructed.To evaluate the hemodynamic environment,the velocity,pressure,time-averaged wall shear stress(TAWSS),and oscillatory shear index(OSI)were calculated.Results A modest quantity of slow flow and recirculation flow was observed in the vicinity of the ulcer-like protrusion(ULP).During the formation of the false lumen,low-velocity blood flow entered the false lumen and resulted in vortex flow.ULPs were located in the region with higher TAWSS,and some high OSIs were found on the ULPs.Conclusion This preliminary study suggests a potential association between the TAWSS or OSI and progression from type B aortic IMH to aortic dissection.
基金Funding The authors acknowledge the National Institute for Occupational Safety and Health(NIOSH)for funding this research project.
文摘Fibrous-type flters are used to capture dust particles in mining and other occupations where personnel are exposed for prolonged periods.Dust cleansing devices including fooded-bed dust scrubbers use these mesh-type multi-layered flters.These flters trap dust particles efciently on their surface and inside their mesh.However,their continued operation leads to dust build-up and clogging.This results in increased resistance of the flter and lowered airfow rate through the scrubber.This could potentially enhance the exposure of the miners.A non-clogging self-cleaning impingement screen type dust flter was designed by the authors for use in mining and industrial dust cleansing applications.The flter guides dirt-laden air through rapidly turning paths which forces it to shed heavier particles.The particles impact one of the impermeable solid metallic flter surfaces and are removed from the airstream.A full cone water spray installed upstream prevents any surface buildup of dust.This paper summaried the computer models generated to show the flter operations and laboratory experiments including optical particle counting to establish the cleaning efciency.
文摘The sensitivity of moving particle semi-implicit(MPS)simulations to numerical parameters is investigated in this study.Although the verifcation and validation(V&V)are important to ensure accurate numerical results,the MPS has poor perfor-mance in convergences with a time step size.Therefore,users of the MPS need to tune numerical parameters to ft results into benchmarks.However,such tuning parameters are not always valid for other simulations.We propose a practical numerical condition for the MPS simulation of a two-dimensional wedge slamming problem(i.e.,an MPS-slamming condition).The MPS-slamming condition is represented by an MPS-slamming number,which provides the optimum time step size once the MPS-slamming number,slamming velocity,deadrise angle of the wedge,and particle size are decided.The simulation study shows that the MPS results can be characterized by the proposed MPS-slamming condition,and the use of the same MPS-slamming number provides a similar fow.
基金supported by the National Research Council of Science&Technology(NST)grant by the Korea government(MSIT)(No.CRC21013)。
文摘This study investigates the accuracy and efficiency of a convolutional autoencoder in predicting flow solutions of diverse characteristics,including strong local nonlinea rity and unsteady wake vortices.Modifications to the standard U-net method were made suitable for non-Cartesian CFD mesh topology,enhancing solution accuracy.Additionally,conditions for predicting flows in unseen environments are integrated into a bottleneck layer between the encoder and decoder structures,guiding flow interpolation or extrapolation and parameter types.For direct comparison,this study uses a proper orthogonal decomposition(POD)-based ROM with linear reconstruction using dominant basis vectors from the flow solution space.Interpolation and extrapolation of generalized coordinates are performed using Gaussian process regression(GPR)and Long Short-Term Memory(LSTM)networks,respectively.The Conditional Unet(CUnet)'s accuracy is demonstrated through inviscid transonic airfoil flows,capturing shock waves effectively.Additionally,it can also be used for predicting the flow field of the three-dimensional shape of the Onera M6 wing.Vortex shedding flows around an Eppler airfoil at a 16-degree angle of attack in turbulent conditions were well-resolved,with root mean squared errors under 1%compared to full-order CFD results.Remarkably,the CUnet's computational efficiency is highlighted as the wall clock CPU time for these 2D flows was less than one second.Finally,the ROM's effectiveness is further validated through successful multi-point shape optimization,minimizing wave drag of RAE 2822 airfoils across subsonic to transonic conditions.This resulted in a maximum drag reduction of 37.38%at Mach 0.74 without performance degradation at off-design conditions.
