We apply the reductive perturbation method to the simple electrostatic ion-temperature-gradient mode in an advanced fluid description. The fluid resonance turns out to play a major role for the excitation of zonal flo...We apply the reductive perturbation method to the simple electrostatic ion-temperature-gradient mode in an advanced fluid description. The fluid resonance turns out to play a major role for the excitation of zonal flows. This is the mechanism recently found to lead to the low-to-high （L-H） mode transition and to the nonlinear Dimits upshift in transport code simulations. It is important that we have taken the nonlinear temperature dynamics from the Reynolds stress as the convected diamagnetic flow. This has turned out to be the most relevant effect as found in transport simulations of the L-H transition, internal transport barriers and Dimits shift. This is the first time that an analytical method is applied to a system which numerically has been found to give the right experimental dynamics.展开更多
An accurate seal forces model is the foundation to analyze the rotor-seal systems. In this paper, the Navier-Stokes equation and energy equation are solved to simulate the interior flow field in the labyrinth seal gap...An accurate seal forces model is the foundation to analyze the rotor-seal systems. In this paper, the Navier-Stokes equation and energy equation are solved to simulate the interior flow field in the labyrinth seal gap. The leakage rate is compared with the experimental results in the literatures. The ：4maximum error is 4% , which proves that the method of employing CFD to simulate the interior flow field of labyrinth seal gap is reliable. Based on this, the interior flow field and fluid exciting force of stage teeth labyrinth seal are studied. By coupling with the Muszynska model, the method of defining the experience loss parameters in Muszynska model is proposed. The results indicate that the experience parameters obtained by the proposed method can depict the nonlinear exciting force of labyrinth seal better.展开更多
Purpose The high-precision detection of vertex detectors in the circular electron positron collider(CEPC)has been a research focus in high-energy physics.However,the vibration characteristics of these detectors under ...Purpose The high-precision detection of vertex detectors in the circular electron positron collider(CEPC)has been a research focus in high-energy physics.However,the vibration characteristics of these detectors under external excitations have not been thoroughly studied.Methods To achieve extremely high spatial resolution,the vertex detector supports(hereafter referred to as the supports)are designed to be lightweight and thin.This study employs theoretical analysis and numerical simulation methods,proposing a multi-objective genetic algorithm to optimize the structural stiffness.The optimized structure is validated through modal analysis and computational fluid dynamics.Results The inner and middle supports exhibit good rigidity,with the first natural frequency exceeding 100 Hz.However,the first natural frequency of the outer support is less than 100 Hz.When subjected to cooling fluid impacts at a flow rate of 4 m/s or higher,this can easily lead to structural resonance.At airflow rates of 2 m/s and 3 m/s,the ratio of the excitation frequency to the natural frequency of the structure exceeds 0.6,resulting in significant vibration amplification.Conclusion The outer support exhibits significant vibration amplification under the impact of cooling airflow at different speeds.By optimizing the structural dimensions and cooling airspeed while ensuring lightweight and structural integrity,this study effectively mitigates the vibration amplification phenomenon in the outer support induced by fluid excitation.展开更多
基金Supported by the JSPS-NRF-NSFC A3 Foresight Program in the Field of Plasma Physics under Grant Nos 11261140328 and 2012K2A2A6000443the ’Thirteenth Five-Year’ Strategic Planning of Chinathe Funds of the Chinese Academy of Sciences and ASIPP
文摘We apply the reductive perturbation method to the simple electrostatic ion-temperature-gradient mode in an advanced fluid description. The fluid resonance turns out to play a major role for the excitation of zonal flows. This is the mechanism recently found to lead to the low-to-high （L-H） mode transition and to the nonlinear Dimits upshift in transport code simulations. It is important that we have taken the nonlinear temperature dynamics from the Reynolds stress as the convected diamagnetic flow. This has turned out to be the most relevant effect as found in transport simulations of the L-H transition, internal transport barriers and Dimits shift. This is the first time that an analytical method is applied to a system which numerically has been found to give the right experimental dynamics.
基金the National Natural Science Foundation of China (Grant No. 10632040)
文摘An accurate seal forces model is the foundation to analyze the rotor-seal systems. In this paper, the Navier-Stokes equation and energy equation are solved to simulate the interior flow field in the labyrinth seal gap. The leakage rate is compared with the experimental results in the literatures. The ：4maximum error is 4% , which proves that the method of employing CFD to simulate the interior flow field of labyrinth seal gap is reliable. Based on this, the interior flow field and fluid exciting force of stage teeth labyrinth seal are studied. By coupling with the Muszynska model, the method of defining the experience loss parameters in Muszynska model is proposed. The results indicate that the experience parameters obtained by the proposed method can depict the nonlinear exciting force of labyrinth seal better.
文摘Purpose The high-precision detection of vertex detectors in the circular electron positron collider(CEPC)has been a research focus in high-energy physics.However,the vibration characteristics of these detectors under external excitations have not been thoroughly studied.Methods To achieve extremely high spatial resolution,the vertex detector supports(hereafter referred to as the supports)are designed to be lightweight and thin.This study employs theoretical analysis and numerical simulation methods,proposing a multi-objective genetic algorithm to optimize the structural stiffness.The optimized structure is validated through modal analysis and computational fluid dynamics.Results The inner and middle supports exhibit good rigidity,with the first natural frequency exceeding 100 Hz.However,the first natural frequency of the outer support is less than 100 Hz.When subjected to cooling fluid impacts at a flow rate of 4 m/s or higher,this can easily lead to structural resonance.At airflow rates of 2 m/s and 3 m/s,the ratio of the excitation frequency to the natural frequency of the structure exceeds 0.6,resulting in significant vibration amplification.Conclusion The outer support exhibits significant vibration amplification under the impact of cooling airflow at different speeds.By optimizing the structural dimensions and cooling airspeed while ensuring lightweight and structural integrity,this study effectively mitigates the vibration amplification phenomenon in the outer support induced by fluid excitation.
