Multi‑physics bi‑directional evolutionary topology optimization on GPU‑architecture

Topology optimization has proven to be viable for use in the preliminary phases of real world design problems. Ultimately, the restricting factor is the computational expense since a multitude of designs need to be considered. This is especially imperative in such fields as aerospace, automotive and biomedical, where the problems involve multiple physical models, typically fluids and structures, requiring excessive computational calculations. One possible solution to this is to implement codes on massively parallel computer architectures, such as graphics processing units (GPUs). The present work investigates the feasibility of a GPU-implemented lattice Boltzmann method for multi-physics topology optimization for the first time. Noticeable differences between the GPU implementation and a central processing unit (CPU) version of the code are observed and the challenges associated with finding feasible solutions in a computational efficient manner are discussed and solved here, for the first time on a multi-physics topology optimization problem. The main goal of this paper is to speed up the topology optimization process for multi-physics problems without restricting the design domain, or sacrificing considerable performance in the objectives. Examples are compared with both standard CPU and various levels of numerical precision GPU codes to better illustrate the advantages and disadvantages of this implementation. A structural and fluid objective topology optimization problem is solved to vary the dependence of the algorithm on the GPU, extending on the previous literature that has only considered structural objectives of non-design dependent load problems. The results of this work indicate some discrepancies between GPU and CPU implementations that have not been seen before in the literature and are imperative to the speed-up of multi-physics topology optimization algorithms using GPUs

A Cross-Validation Approach to Approximate Basis Function Selection of the Stall Flutter Response of a Rectangular Wing in a Wind Tunnel

The stall flutter response of a rectangular wing in a low speed wind tunnel is modelled using a nonlinear difference equation description. Static and dynamic tests are used to select a suitable model structure and basis function. Bifurcation criteria such as the Hopf condition and vibration amplitude variation with airspeed were used to ensure the model was representative of experimentally measured stall flutter phenomena. Dynamic test data were used to estimate model parameters and estimate an approximate basis function

Limit cycle oscillations of cantilever rectangular flat plates in a wind tunnel

A closed form state-space model of the nonlinear aeroelastic response of thin cantilevered flat plates is derived using a combination of Von Karman thin plate theory and a linearized continuous time vortex lattice aerodynamic model. The modal-based model is solved for the amplitude and period of the limit cycles of the flat plates using numerical continuation. The resulting predictions are compared to experimental data obtained from identical flat plates in the wind tunnel. It is shown that the aeroelastic model predicts the linear flutter conditions and nonlinear response of the plates with reasonable accuracy, although the predicted limit cycle amplitude variation with airspeed is different to the one measured experimentally due to unmodelled physics

Damping identification in a non-linear aeroelastic structure

An energy-based method is proposed to identify damping parameters from time histories of responses to sets of single-frequency harmonic excitation. The method is intended to be practically applicable to real structures and is able to identify the value of viscous damping, Coulomb friction and eventually other forms of non-linear damping models in aeroelastic systems. The inputs required are simply the accelerometer signals and the forces applied. It will be shown that if the system is undergoing Limit Cycle Oscillations, no external force is required for the identification process

Transient Temperature Effects on the Aerothermoelastic Response of a Simple Wing

Aerothermoelasticity plays a vital role in the design and optimisation of hypersonic aircraft. Furthermore, the transient and nonlinear effects of the harsh thermal and aerodynamic environment a lifting surface is in cannot be ignored. This article investigates the effects of transient temperatures on the flutter behavior of a three-dimensional wing with a control surface and compares results for transient and steady-state temperature distributions. The time-varying temperature distribution is applied through the unsteady heat conduction equation coupled to nonlinear aerodynamics calculated using 3rd order piston theory. The effect of a transient temperature distribution on the flutter velocity is investigated and the results are compared with a steady-state heat distribution. The steady-state condition proves to over-compensate the effects of heat on the flutter response, whereas the transient case displays the effects of a constantly changing heat load by varying the response as time progresses

A Generic Model for Benchmark Aerodynamic Analysis of Fifth-Generation High-Performance Aircraft

This paper introduces a generic model for the study of aerodynamic behaviour relevant to fifth-generation high-performance aircraft. The model design is presented, outlining simplifications made to retain the key features of modern high-performance vehicles while ensuring a manufacturable geometry. Subsonic wind tunnel tests were performed with force and moment balance measurements used to develop a database of experimental validation data for the platform at a freestream velocity of 20 m/s. Numerical simulations are also presented and validated by the experiments and further employed to ensure the vortex behaviour is consistent with contemporary high-performance platforms. A sensitivity study of the computational predictions from the turbulence modelling approach is also presented. This geometry is the first in a suite of representative aircraft geometries (the Sydney Standard Aerodynamic Models), in which all geometries, computational models, and experimental data are made openly available to the research community (accessible via this link: https://zenodo.org/communities/ssam_gen5/) to serve as validation test cases and promote best practices in aerodynamic modelling

Drag Minimisation Using Adaptive Aeroelastic Structures

This paper describes the latest developments in a research program investigating the development of “adaptive internal structures” to enable adaptive aeroelastic control of aerospace structures. Through controlled changes of the second moment of area, orientation or position of the spars, it is possible to control the bending and torsional stiffness characteristics of aircraft wings or tail surfaces. The aeroelastic behaviour can then be controlled as desired. A number of different adaptive internal structure concepts (rotating, moving and split spars) are compared here using a simple rectangular wing structure in order to determine which are the most effective for achieving minimum drag at different points in a representative flight envelope. A genetic algorithm approach is employed to determine the optimal spar orientation for rotating spars concept. It is shown that it is feasible to adjust the structure and trim characteristics of such wing structures in order to achieve minimum drag at all conditions