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Computation of Stiffness and Damping Derivatives of an Ogive in a Limiting Case of mach number and Specific Heat Ratio

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Fluid Dynamics & Materials Processing 2023年第5期19卷 1249-1267页

作者： Aysha Shabana Asha Crasta Sher Afghan Khan Abdul Aabid Muneer Baig Department of Mathematics Mangalore Institute of Technology and EngineeringMoodabidri574225India Department of Mathematics Sahyadri College of Engineering&ManagementMangalore575007India Department of Mechanical and Aerospace Engineering Faculty of EngineeringInternational Islamic UniversityKuala Lumpur53100Malaysia Department of Engineering Management College of EngineeringPrince Sultan UniversityRiyadh11586Saudi Arabia

This work aims to compute stability derivatives in the Newtonian limit in pitch when the mach number tends to *** such conditions,these stability derivatives depend on the Ogive’s shape and not the mach ***,the mach number independence principle becomes effective from M=10 and *** Ogive nose is obtained through a circular arc on the cone ***,the following arc slopes are consideredλ=5,10,15,−5,−10,and−*** is found that the stability derivatives decrease due to the growth inλfrom 5 to 15 and vice ***λ=5 and 10,the damping derivative declines with an increase inλfrom 5 to ***,for the damping derivatives,the minimum location remains at a pivot position,h=0.75 for large values ofλ.Hence,whenλ=−15,the damping derivatives are independent of the cone angles for most pivot positions except in the early twenty percent of the leading edge.

关键词： Aerodynamic stability derivative mach number specific heat ratio Ogive

mach number Prediction Models Based On Ensemble Neural Networks for Wind Tunnel Testing

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Mach Number Prediction Models Based On Ensemble Neural Netwo...

第26届中国控制与决策会议

作者： ZhiWei Jin Li Zhao ZhengZhou Rao High Speed Aerodynamics Institute China Aerodynamics Research and Development Center

The 2.4m×2.4m wind tunnel is a system with the properties of strong nonlinear, multiple variables, serious coupling, large lagging, time-varying, etc. The complexity of all these phenomena makes the development of suitable dynamic mach number models based on the aerodynamics laws very difficult. As an alternative, the Ensemble Neural Networks（ENN） model based on the feature subsets is proposed to address this problem. ENN built the sub-models on different lower dimension data sets, and reduced the complexity of the single Neural Networks（NN） built on the whole data set. Furthermore, a comparative study among the single NN models and the ENN models when used to predict the mach number is conducted. Results show that the performance is improved by the ENN models. It is also shows that training time and testing time are much reduced by the ENN models.

关键词： Wind tunnel mach number Ensemble Neural Networks.

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高马赫数球状气泡动力学理论研究

哈尔滨工程大学学报（英文版） 2024年第1期23卷 39-48页

作者：韩泠西颜帅李帅 College of Shipbuilding Engineering Harbin Engineering UniversityHarbin 150001China

The compressibility of fluids has a profound influence on oscillating bubble dynamics,as characterized by the mach ***,current theoretical frameworks for bubbles,whether at the first or second order of the mach number,are primarily confined to scenarios characterized by weak ***,a critical need to elucidate the precise range of applicability for both first-and second-order bubble theories ***,we investigate the suitability and constraints of bubble theories with different orders through a comparative analysis involving experimental data and numerical *** focal point of our investigation encompasses theories such as the Rayleigh–Plesset,Keller,Herring,and second-order bubble ***,the impact of parameters inherent in the second-order equations is *** spherical oscillating bubble dynamics in a free field,our findings reveal that the first-and second-order bubble theories are applicable when Ma≤0.3 and 0.4,*** a single sonoluminescence bubble,we define an instantaneous mach number,*** second-order theory shows abnormal sensibility when Mai is high,which is negligible when Mai≤*** results of this study can serve as a valuable reference for studying compressible bubble dynamics.

关键词： Bubble dynamics Spherical bubble Cavitation Compressibility mach number

Numerical Analysis of Cavity-Based Control of Base Pressure Variations at Supersonic mach numbers

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Fluid Dynamics & Materials Processing 2023年第6期19卷 1655-1677页

作者： Ridwan Sher Afghan Khan Jaffar Syed Mohamed Ali Mohd.Azan Mohammed Sapardi Abdul Aabid Mechanical and Aerospace Engineering Department Faculty of EngineeringInternational Islamic UniversityKuala Lumpur53100Malaysia Department of Engineering Management College of EngineeringPrince Sultan UniversityRiyadh11586Saudi Arabia

In the present study,the base pressure variations induced by the presence of a cavity,known to have a strong influence of the behaviour of supersonic projectiles,are investigated through numerical solution of the balance equations for mass,momentum,and *** area ratio of four is considered and numerical simulations are carried out at mach M=1.2,1.4,1.6,and 1.8 assuming no cavity or cavity locations 0.5D,1D,1.5D,and *** inlet pressure of the nozzle is considered as a flow *** Taguchi method is also used,and the considered cases are then analyzed using a full factorial experimental *** results show that the cavity is effective in increasing the base pressure for the conditions *** other nozzle pressure ratios,cavities do not lead to passive control due the change in the reattachment *** distribution of wall pressure reveals that,in general,a cavity used to implement passive control of the base pressure does not adversely influence the flow pattern in the domain.

关键词： mach number cavity Taguchi base flow base drag

A numerical study of segmented cooling-stream injection in supersonic film cooling

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Chinese Journal of Aeronautics 2022年第6期35卷 156-171页

作者： Hang NI Mingjun WANG Peixue JIANG Wei PENG Yinhai ZHU Institute of Nuclear and New Energy Technology Collaborative Innovation Center of Advanced Nuclear Energy TechnologyKey Laboratory of Advanced Reactor Engineering and Safety of Ministry of EducationTsinghua UniversityBeijing 100084China School of Nuclear Science and Technology Xi’an Jiaotong UniversityXi’an 710049China Department of Energy and Power Engineering Key Laboratory for Thermal Science and Power Engineering of Ministry of EducationTsinghua UniversityBeijing 100084China Tsinghua University-Zhang Jiagang Joint Institute for Hydrogen Energy and Lithium-Ion Battery Technology Tsinghua UniversityBeijing 100084China

The present study proposes a segmented cooling-stream injection structure based on a certain coolant mass flow rate,and numerically investigates the effect of segmented cooling-stream injection on supersonic film *** results indicate that without shock-wave impingement and with helium as the coolant,segmented cooling-stream injection can reduce the mixing between the mainstream and the cooling stream to produce better cooling performance than single injection,especially at larger coolant mach ***,with nitrogen as the coolant,the cooling effect of the segmented-injection system is very close to that of the single-injection *** at the impinging region is enhanced significantly when there is an incident shock *** the shock wave impinges between the two coolant inlets,segmented cooling-stream injection improves film cooling effectiveness in the midstream and downstream regions more than single injection because only part of the cooling stream undergoes the enhanced mixing effect of the shock *** advantage of segmented injection is reduced when the impinging region is behind the second coolant *** further downstream the impinging region,the smaller the associated advantage.

关键词： Film cooling mach number Segmented injection Shock wave Supersonic flow

Incompressible Limit of the Compressible Q-tensor System of Liquid Crystals

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Acta Mathematicae Applicatae Sinica 2023年第1期39卷 179-201页

作者： Yi-xuan WANG University of Pittsburgh PA 15260USA

We study the connection between the compressible Navier-Stokes equations coupled by the Qtensor equation for liquid crystals with the incompressible system in the periodic case, when the mach number is low. To be more specific, the convergence of the weak solutions of the compressible nematic liquid crystal model to the incompressible one is proved as the mach number approaches zero, and we also obtain the similar results in the stochastic setting when the equations are driven by a stochastic force. Our approach is based on the uniform estimates of the weak solutions and the martingale solutions, then we justify the limits using various compactness criteria.

关键词： compressible liquid crystal system Q-tensor weak solutions martingale solution stochastic compactness mach number incompressible limit

Modeling and Validation of Base Pressure for Aerodynamic Vehicles Based on machine Learning Models

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Computer Modeling in Engineering & Sciences 2023年第12期137卷 2331-2352页

作者： Jaimon Dennis Quadros Sher Afghan Khan Abdul Aabid Muneer Baig Senior Lecturer of Mechanical Engineering University of BoltonRAK Academic CenterRas Al Khaimah16038UAE Department of Mechanical and Aerospace Engineering Faculty of EngineeringInternational Islamic University MalaysiaSelangor53100Malaysia Department of Engineering Management College of EngineeringPrince Sultan UniversityRiyadh11586Saudi Arabia

The application of abruptly enlarged flows to adjust the drag of aerodynamic vehicles using machine learning models has not been investigated *** process variables(mach number(M),nozzle pressure ratio(η),area ratio(α),and length to diameter ratio(γ))were numerically explored to address several aspects of this process,namely base pressure(β)and base pressure with cavity(βcav).In this work,the optimal base pressure is determined using the PCA-BAS-ENN based algorithm to modify the base pressure presetting accuracy,thereby regulating the base drag required for smooth flow of aerodynamic *** on the identical dataset,the GA-BP and PSO-BP algorithms are also compared to *** data for training and testing the algorithmswas derived using the regression equation developed using the Box-Behnken Design(BBD).The results show that the PCA-BAS-ENN model delivered highly accurate predictions when compared to the other two *** a result,the advantages of these results are two-fold,providing:(i)a detailed examination of the efficiency of different neural network algorithms in dealing with a genuine aerodynamic problem,and(ii)helpful insights for regulating process variables to improve technological,operational,and financial factors,simultaneously.

关键词： High speed flow mach number machine learning PCA-BAS-ENN algorithm

Numerical Analysis of a Microjet-Based Method for Active Flow Control in Convergent-Divergent Nozzles with a Sudden Expansion

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Fluid Dynamics & Materials Processing 2022年第6期18卷 1877-1900页

作者： Abdul Aabid Sher Afghan Khan Muneer Baig Department of Engineering Management College of EngineeringPrince Sultan UniversityRiyadh11586Saudi Arabia Department of Mechanical Engineering Faculty of EngineeringInternational Islamic University MalaysiaKuala Lumpur50728Malaysia

A method based on microjets is implemented to control the flow properties in a convergent-divergent nozzle undergoing a sudden *** different variants of this active control technique are explored numerically by means of a finite-volume method for compressible fluid flow:with the first one,the control is implemented at the base,with the second at the wall,while the third one may be regarded as a combination of *** jets are over-expanded,the control is not very ***,when a favourable pressure gradient is established in the nozzle,the control becomes effective,leading to an increase in the base pressure.

关键词： Base pressure supersonic flow CFD mach number microjet control

Computational Analysis of Surface Pressure Distribution over a 2D Wedge in the Supersonic and Hypersonic Flow Regimes

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Fluid Dynamics & Materials Processing 2023年第6期19卷 1637-1653页

作者： Javed S.Shaikh Krishna Kumar Khizar A.Pathan Sher A.Khan MIT School of Engineering MIT ADT UniversityPune412201India Trinity College of Engineering and Research Pune411048India Department of Mechanical Engineering International Islamic University MalaysiaKuala Lumpur53100Malaysia

The complex fluid-dynamic instabilities and shock waves occurring along the surface of a two-dimensional wedge at high values of the mach number are studied here through numerical solution of the governing ***,a regression model is implemented to determine the pressure distribution for various mach numbers and angles of *** mach number spans the interval from 1.5 to *** wedge angles(θ)are from 5°to 25°.The pressure ratio(P2/P1)is reported at various locations(x/L)along the 2D *** results of the numerical simulations are compared with the regression model showing good agreement.

关键词： CFD analysis supersonic wedge angle mach number