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AIAA Science and Technology (SciTech) Forum and Exposition

作者： Goodwin, Gabriel B. Bachman, Christian L. Oran, Elaine S. Kaplan, Carolyn R. Sosa, Jonathan Ahmed, Kareem A. Naval Res Lab Naval Ctr Space Technol Code 8221 Washington DC 20375 USA Univ Maryland Dept Aerosp Engn College Pk MD 20742 USA Univ Cent Florida Dept Mech & Aerosp Engn Orlando FL 32816 USA

ISBN: (数字)9781624105784

ISBN: (纸本)9781624105784

Detonation waves are an extremely efficient mechanism for burning fuel-air mixtures to release their chemical energy and generate thrust in high-speed airbreathing engines. In standing detonation wave engines, one of the major challenges is sustaining a stable, standing detonation wave within the combustor. Experiments at the University of Central Florida (UCF) have studied the propagation of detonation waves injected orthogonally into Mach 5 flows of premixed hydrogen and air. This paper focuses on numerical simulations of detonation propagation in the experimental facility with fuel equivalence ratios of 0.85 and 0.70. The compressible reactive Navier-Stokes equations are solved by a high-order numerical algorithm on a locally adapting mesh. In the range of conditions studied, the overdriven detonations injected into the crossflow decoupled into shocks and flames. Subsequent detonations occurred through shock reflections and shock-flame interactions. The survivability of the subsequent detonations was observed to be highly dependent on the fuel equivalence ratio and wall boundary conditions.

关键词： Detonation Waves Deflagration to Detonation Transition Chemical Energy Combustors Navier Stokes Equations numerical Simulation Detonation Wave Engines High Speed Airbreathing Engines numerical algorithms Flow Conditions

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Ultra-fast high order unsteady simulations on GPUs based on a new computational model

Ultra-fast high order unsteady simulations on GPUs based on ...

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AIAA Aviation Forum and Exposition

作者： Liu, Kai Lu, Yi Dimaxer Technol KK Osaka Japan Dimaxer Technol Ltd Cambridge CB23 6DP England

ISBN: (数字)9781624105890

ISBN: (纸本)9781624105890

A new computational model is introduced in this work, which packs all high order space-time computational operations as separated units called Magazines with all dependent data on CPUs, and send/receive to GPUs for calculation in completely asynchronous mode. The non-stopping time-marching controller simply keep all CPUs preparing Magazines and GPUs calculating evolutions of available Magazines simultaneously. This computational model is able to overcome the size limitation of device memory on GPUs by storing all data on main RAMs which basically accessed by CPUs and only relatively small size Magazines need to be temporarily stored on GPU memory. The size of each Magazine is very flexible which means this model is suited for different heterogeneous computing systems. The feasibility of this model is based on the special features of our innovative space time expansion of high order kinetic preserving flux reconstruction (STE-KEP-FR) method. Hundreds of simulations for Tylor-Green vortex case at Re = 1600 were performed and analyzed by solving both compressible NS equations and incompressible NS equations in Entropically Damped Artificial Compressibility(EDAC) formula, using different orders of accuracy polynomial reconstructions on uniform conformal, nonuniform nonconformal, and overset meshes respectively to test accuracy, robustness (stability), computational speed and the ability to handle realistic complex geometries. The flow passing sphere case at Re = 10(4) and Re = 10(6) were performed on both conformal mesh with non-conformal refinement, and overset mesh to test the solver speed for simulations with wall boundaries. The nearly 100% computing ability usages of multi-GPUs were achieved for nearly all simulations with order of accuracy higher than 5th.

关键词： Computing Architecture Taylor Green Vortex CFD Simulation Kinetic Energy Incompressible Flow Navier Stokes Equations numerical algorithms Mach Number Pseudo Spectral Method Runge Kutta Methods

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Advances in Output Feedback Control of Transient Energy Growth in a Linearized Channel Flow

Advances in Output Feedback Control of Transient Energy Grow...

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AIAA Science and Technology (SciTech) Forum and Exposition

作者： Yao, Huaijin Hemati, Maziar S. Univ Minnesota Aerosp Engn & Mech Minneapolis MN 55455 USA

ISBN: (数字)9781624105784

ISBN: (纸本)9781624105784

Transient energy growth (TEG) is a primary mechanism for bypass transition in many wall-bounded shear flows. Here, we investigate the efficacy of reducing TEG in a linearized channel flow with feedback controllers that use wall shear-stress sensors and wall-normal blowing/suction actuators. Owing to established performance limitations of observer-based controller designs within the context of TEG, we study static output feedback linear quadratic regulation (SOF-LQR) strategies for control. SOF-LQR is found to outperform optimal observer-based feedback designs, and to reduce TEG of spanwise disturbances relative to the uncontrolled flow. We further show that by introducing an appropriate set of additional observables, SOF-LQR controllers can reduce TEG associated with streamwise and oblique disturbances as well. In fact, we show that by selecting a small number of appropriate observables, SOF-LQR controllers can fully recover full-state LQR performance.

关键词： Full State Feedback Channel Flow Linear Quadratic Regulator Sensor Technology Shear Stress Actuators Algebraic Riccati Equation Navier Stokes Equations numerical Simulation numerical algorithms

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The compact Green's function for multiple bodies 25

The compact Green's function for multiple bodies

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25th AIAA/CEAS Aeroacoustics Conference

作者： Baddoo, P. J. Ayton, L. J. Ctr Math Sci Dept Appl Math & Theoret Phys Wilberforce Rd Cambridge CB3 0WA England

ISBN: (数字)9781624105883

ISBN: (纸本)9781624105883

The acoustic emissions of compact bodies may be analysed using the compact Green's function. Whilst it is straightforward to construct the compact Green's function for single bodies, the construction for multiple bodies is far more challenging. In this paper, we present analytic solutions for the compact Green's function for multiple bodies. By writing the solution in terms of the transcendental Schottky-Klein prime function, the compact Green's function has exactly the same functional form for any number of bodies in the system. Moreover, the formulation permits the inclusion of a low Mach number background flow. The compact Green's function is illustrated for some simple examples for flat plates and cylinders and the sound generation of a Kasper wing is considered in detail.

关键词： Green's Function Mach Number Acoustic Emission Potential Flow Vortex Dynamics Angle of Attack Kutta Condition Take off and Landing numerical algorithms Aeroacoustics

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numerical Stackelberg Solutions in a Class of Positional Differential Games

Numerical Stackelberg Solutions in a Class of Positional Dif...

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17th IFAC Technical-Committee-on-Optimal-Control (TC 2.4) Workshop on Control Applications of Optimization (CAO)

作者： Kuvshinov, Dmitry R. Osipov, Sergei I. Yeltsin Ural Fed Univ Krasovsky Inst Math & Mech Ekaterinburg Russia Yeltsin Ural Fed Univ Ekaterinburg Russia

We consider a problem of numerical construction of a Stackelberg solution in a differential game with closed-loop information structure and terminal player payoffs. It is divided into two subproblems: the problem of computing of so-called "admissible" motions and the optimization problem on the set of admissible motions. We focus on the latter problem and consider two approaches: enumeration of the follower player payoffs and enumeration of the leader player payoffs. algorithms implementing both approaches are presented and tested on a model system. (C) 2018, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.

关键词： Differential games Stackelberg games numerical algorithms

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Latent hardening within the elasto-plastic self-consistent polycrystal homogenization to enable the prediction of anisotropy of AA6022-T4 sheets

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INTERNATIONAL JOURNAL OF PLASTICITY 2018年 105卷 141-163页

作者： Zecevic, Milovan Knezevic, Marko Univ New Hampshire Dept Mech Engn 33 Acad WayKingsbury Hall W119 Durham NH 03824 USA

Slip system hardening behavior of a given slip system is influenced more by shearing on another slip system known, as latent hardening, than by shearing on itself, known as self-hardening. This paper extends a recently developed dislocation-based hardening law within the elasto-plastic self-consistent polycrystal plasticity model to incorporate the latent hardening effects for predicting anisotropic response of polycrystalline face-centered cubic metals. In doing so, a new approach to overcome singularities associated with the self-consistent Eshelby solution procedure is proposed. The new approach is validated using a regularized Schmid law, where the singularity in Eshelby tensor calculation is intrinsically suppressed. Moreover, the solution procedure for single crystal stress increment is advanced to be based on a methodology involving the singular value decomposition to solve for shear increments. It is found that modeling crystallographic texture evolution and latent hardening successfully captures the anisotropic behavior of polycrystalline AA6022-T4 alloy. The model is subsequently successfully applied to predict large strain cyclic deformation of the same material. The implementation and insights from these predictions are presented and discussed in this paper.

关键词： Microstructures Crystal plasticity Polycrystalline material numerical algorithms AA6022-T4

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Nonsingular Sliding-Mode Control for Field-of-View Constrained Impact Time Guidance

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2018年第5期41卷 1214-1222页

作者： Chen, Xiaotian Wang, Jinzhi Peking Univ State Key Lab Turbulence & Complex Syst Dept Mech & Engn Sci Coll Engn Beijing 100871 Peoples R China

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Understanding thermally-activated glide of 1/2⟨110⟩{110} screw dislocations in UO₂ - A molecular dynamics analysis

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INTERNATIONAL JOURNAL OF PLASTICITY 2018年 110卷 294-305页

作者： Lunev, A., V Starikov, S., V Aliev, T. N. Tseplyaev, V., I Russian Acad Sci Joint Inst High Temp 13 Bld 2Izhorskaya St Moscow 125412 Russia UKAEA Culham Sci Ctr Abingdon OX14 3DB Oxon England State Res Ctr Russian Federat Troitsk Inst Innovat & Fus Res SRC RF TRINITI Troitsk 142190 Moscow Reg Russia

As shown experimentally, the interplay between screw and edge dislocations in uranium dioxide (UO2) determines the low-temperature plasticity in this material. For the latter, neither the mobility of screw dislocations nor the mechanisms of their glide had been assessed - up until now. It is particularly interesting to evaluate the mobility of 1/2(< 110 >{110} screw dislocations, supposedly the least mobile in UO2 due to the allegedly extremely high Peierls barrier of their motion. To address this issue, molecular dynamics simulations of dislocation glide are conducted on Lomonosov/MVS-10P supercomputers with LAMMPS software, and post-processing is done using DXA/OVITO. Under changing temperature and stress, the following variations of thermally-activated glide are found: nucleation and expansion of double kinks, formation and recombination of 1/6 < 112 > Shockley partials, self-pinning and production of debris, formation of sessile 1/3 < 111 > Frank loops. Velocity function of 1/2 < 110 >{110} dislocations calculated at temperatures T = 500-2000 K and shear stresses sigma = 10-1000 MPa shows a weak temperature dependence and becomes higher than the velocity of 1/2 < 110 >{001} edge dislocations at temperatures T < 1250 K.

关键词： Dislocations Ceramic material numerical algorithms Atomistic simulation

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Multilevel Algorithm for Obtaining the Proper Orthogonal Decomposition

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AIAA JOURNAL 2018年第11期56卷 4423-4436页

作者： Behzad, Fariduddin Helenbrook, Brian T. Ahmadi, Goodarz Clarkson Univ Dept Mech & Aeronaut Engn 8 Clarkson Ave Potsdam NY 13699 USA Clarkson Univ Dept Mech & Aeronaut Engn Engn Sci Simulat 8 Clarkson Ave Potsdam NY 13699 USA Clarkson Univ Dept Mech & Aeronaut Engn Mech & Aeronaut Engn 8 Clarkson Ave Potsdam NY 13699 USA

A multilevel proper orthogonal decomposition (mPOD) is introduced for obtaining the proper orthogonal decomposition (POD) of data sets with a large number of snapshots without requiring the solution of an equally large eigenvalue problem. mPOD works by producing the PODs for subsets of data first and then applying the POD again to the modes obtained from these subsets. A proof is given that mPOD reproduces identically the modes that would be obtained with the standard POD. mPOD also provides a systematic way to combine POD modes obtained from different simulations and to update POD modes using new data. A numerical algorithm based on mPOD is developed that shows a factor of 10 reduction in computation time compared to snapshot POD. The method is applied to data for fluid flow over a NACA 0015 at Re = 1000 with an actuator jet on the top surface of the airfoil, and results are compared to methods such as subsampling, double proper orthogonal decomposition, sequential mode generation methods, recursive singular value decomposition (R-SVD), and partitioned R-SVD. The examples demonstrate that mPOD provides more accurate eigenvalues, requires fewer disk accesses, and generates modes that create more reliable reduced-order models and have better orthogonality properties than any of the other methods.

关键词： Singular Value Decomposition NACA 0015 Velocity Profiles Actuators numerical algorithms Vortex Shedding Direct numerical Simulation Incompressible Viscous Flow MATLAB Finite Element Method

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Fracture Cross Extension Arithmetic Research Based on Non-continuum Theory

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WIRELESS PERSONAL COMMUNICATIONS 2018年第1期103卷 41-53页

作者： Wang, Suling Jiang, Minzheng Dong, Kangxing Chen, Mingzhan Northeast Petr Univ Mech Sci & Engn Coll Daqing 163318 Heilongjiang Peoples R China Daqing Oilfield Co LTD Daqing 163300 Heilongjiang Peoples R China

The cross extension of hydraulic fracture and natural fracture is the key to realize the volume fracture in unconventional reservoir. Based on the non-continuum theory, with the help of numerical simulation algorithm, a mathematical model for in-situ stress about fracturing expansion when the hydraulic fracture intersects with a natural fracture is presented. Then, using two-dimensional linear elastic theory verify the validity of degenerate in-situ stress mode. So it makes the natural fissure error about natural fracture surface pressure less than 1%. As a result, the accuracy of the model was proved. On the basis of the above, considering fluid-structure coupling effect, the stress change rules on natural fracture surface are obtained during hydraulic fracture extension process. The calculation results are as follows: In the process of hydraulic fracture approaching natural fracture, the surface of natural fracture occurs shear deformation first, and then turns into open deformation. Under the influence of shear deformation, the direction of the maximum principal stress on natural fracture surface is the same as initial horizontal maximum principal geostress. Due to the expansion of hydraulic fracture and fracture tip concentration effect, the maximum principal stress appears in the hydraulic fracture tip, this two points may induce the natural fracture begin to extend. And for initial ground stress in a stratum, the smaller the difference, the greater the pressure required to open the natural fracture. At this time, the maximum principal stress on the surface of the natural fracture is less concentrated;multiple fracture initiations are easily formed. Under high pressure, when the approaching angle between natural fracture and hydraulic fracture closes to 45 degrees hydraulic fracture is easier to activate natural fracture, the formed hydraulic fracture shape is more complicated.

关键词： numerical algorithms Natural fracture Shear slip Fracture diverting Initial ground stress difference Approaching angle

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