Raymond P. LeBeau

Numerical study of blowing and suction control mechanism on NACA0012 airfoil

A jet with a width of 2.5% the chord length is placed on a NACA0012 airfoil’s upper surface simulating the blowing and suction control under Re =5 × 10 5 and angle-of-attack 18-deg conditions. Nearly 300 numerical simulations are conducted over a range of parameters (jet location, amplitude, and angle). The physical mechanisms that govern suction and blowing flow control are determined and analyzed, and the critical values of suction and blowing locations, amplitudes, and angles are discussed. The current successful large-scale numerical studies create a useful knowledge base for further exploration of multijet control system.

Optimization of Airfoil Flow Control Using a Genetic Algorithm with Diversity Control

The aerospace community is on the verge of a new generation of practical active flow control devices, from synthetic jets to plasma actuators. However, even as the mechanical challenges of implementing these systems seem attainable, the proper placement, orientation, and energy inputs to achieve the maximum benefit in a variety of flow conditions are often poorly known. Successful application of computational fluid dynamics to this type of control problem critically depends on an efficient searching algorithm for design optimization. Based on our previous research of single-suction/blowing-jet control on a NACA 0012 airfoil, the design parameters of a test two-jet system are proposed. A genetic algorithm drives the computational fluid dynamics simulations, guiding the configuration of a suction jet and a blowing jet on the airfoils upper surface. Reasonable optimum control values are determined within the control parameter range, and the sensitivity of the control values can be determined through a comparison of the fitness value from a large number of computational fluid dynamics simulations.

A Cell-Centered Pressure Based Method for Two/Three- Dimensional Unstructured Incompressible Navier-Stokes Solver

*† ‡ A cell-centered pressure based method is presented in this paper, and it is implemented in a new two/three-dimensional parallel unstructured CFD code to meet the challenges of physical problems with complex geometries and complicated boundary conditions while maintaining high computational efficiency. The method uses a second order upwind scheme in space and a second order backward scheme for time accuracy. The SIMPLE algorithm in conjunction with the Rhie and Chow approach solves the continuity equation, minimizing undesirable pressure oscillations. The code is parallelized using METIS domain decomposition with good load balancing across computational nodes. In order to demonstrate the accuracy and performance of the current cell-centered pressure based method, several test cases are presented for validation such as two-dimensional incompressible flow past a flat plate, two/three-dimensional driven cavity flow, and two/three-dimensional flow over a circular cylinder. Notably, an extensive qualitative and quantitative study of two-dimensional flow over a circular cylinder for low Reynolds number is also presented in this paper.

High-Cost CFD on a Low-Cost Cluster

Direct numerical simulation of the Navier-Stokes equations (DNS) is an important technique for the future of computational fluid dynamics (CFD) in engineering applications. However, DNS requires massive computing resources. This paper presents a new approach for implementing high-cost DNS CFD using low-cost cluster hardware. After describing the DNS CFD code DNSTool, the paper focuses on the techniques and tools that we have developed to customize the performance of a cluster implementation of this application. This tuning of system performance involves both recoding of the application and careful engineering of the cluster design. Using the cluster KLAT2 (Kentucky Linux Athlon Testbed 2), while DNSTool cannot match the

Use of Cache-Friendly Blocking to Accelerate CFD Codes on Commodity Hardware

0.64 per MFLOPS that KLAT2 achieves on single precision ScaLAPACK, it is very efficient; DNSTool on KLAT2 achieves price/performance of

OPTIMIZATION OF BLOWING AND SUCTION CONTROL ON NACA 0012 AIRFOIL USING GENETIC ALGORITHM

2.75 per MFLOPS double precision and

Joint Performance Evaluation and Optimization of Two CFD Codes on Commodity Clusters

1.86 single precision. Further, the code and tools are all, or will soon be, made freely available as full source code.

Applying Genetic Algorithms to Complex Computational Fluid Dynamics Simulations

This paper presents an analysis of performance improvement of two CFD codes, the structured two-dimensional code GHOST and the unstructured two-/three-dimensional code UNCLE, both in-house codes at the University of Kentucky, with the specific target of cache performance optimization. The primary technique of choice is the blocking of data arrays, either within specific subroutines or of the computational grid as a whole. Both methods have produced significant improvements in performance without compromising accuracy. More advanced 64-bit commodity hardware reduces some of the relative gain from blocking due to its improved bandwidth and memory structure, but significant gains in performance are still seen. This study suggests that as cache sizes continue to increase, blocking may prove a general useful tool for accelerating CFD code performance.

Application of Genetic Algorithm to Two-jet Control System On NACA 0012 Airfoil

Active control of the flows over airfoil is an area of heightened interest in the aerospace community. Previous research on flow control design processes heavily depended on trial and error and the designers’ knowledge and intuition. Such an approach cannot always meet the growing demands of higher design quality in less time. Successful application of computational fluid dynamics (CFD) to this kind of control problem critically depends on an efficient searching algorithm for design optimization. Based on our previous research of single suction/blowing jet control on a NACA 0012 airfoil, the design parameters of a two-jet system are proposed. A realcoded EARND genetic algorithm is built on top of the CFD code, guiding the movement of a suction jet and a blowing jet along the airfoil’s upper surface. The reasonable optimum control values are determined within the control parameter range. The current study of Genetic Algorithm on airfoil flow control has been demonstrated to be a successful optimization application.

Examination of Three-Dimensional Flow over a Chambered Inflatable Wing

The performance analysis of computational fluid dynamics code can yield unexpected results, and translating the performance data into code improvements is not always a straightforward task. A possible approach for increasing comprehension is to look at the performance of multiple codes simultaneously. In this manner, differences in the codes may be connected to differences in the performance, allowing for the better methodology to be adopted across the codes. This paper presents such a comparative analysis for two CFD codes, the structured two-dimensional code GHOST and the unstructured two-/three-dimensional code UNCLE, both in-house codes at the University of Kentucky. These codes are used regularly across several commodity cluster platforms, two of which are briefly described. This paper presents the initial performance evaluation of these codes followed by a discussion of some of the optimization techniques applied and the resulting changes in performance.