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AHPCRC Bulletin: Summer 1997 - Volume 7 Number 3

1997 Summer Undergraduate Internship Program in HPC in Fluid Dynamics

Mark Wibben (UM)

The Summer of 1997 marked the 3rd year that the AHPCRC co-sponsored, along with the National Science Foundation, an undergraduate Summer Internship Program. The Program was designed to encourage undergraduate participation in High Performance Computing (HPC) in Fluid Dynamics, and train future scientists and engineers in HPC research. This past summer there were six participants, each of whom completed a project supervised by an AHPCRC researcher. Projects involved the use of HPC to solve real-world problems in science and engineering. The following students spent ten weeks in Minneapolis working on the projects described.

Figure 1. Pressure contours in flows past a solid propellant.
Jennifer Jackson is pursuing a degree from Yale University in Chemical Engineering. Her supervisors for the project "Finite Element Simulation of Fluid Flows and Moving Structures" were Stephen Ray and Tayfun Tezduyar (AHPCRC-University of Minnesota [UM]), and Gloria Wren (Propulsion and Flight Division of the Army Research Laboratory Weapons and Materials Research Directorate). The objective was to use finite element methods to model flow past a movable solid object and understand how the motion of the solid object affected the flow. The specific problem worked on was a solid propellant gun, which is being studied by the US Army.

The flow in this problem was compressible and governed by the Navier-Stokes equations. In Figure 1, the pressure contours in flows past the solid propellant during the firing of the gun are shown. Simulations were run on the CRAY C90 and the Thinking Machines CM-5. The mesh generator and flow solver used in this project were developed by the Team for Advanced Flow Simulation and Modeling (T*AFSM).

Figure 2. Model of a helicopter with the surface element faces shaded and outlined.
Brian Matheis is pursuing a degree from Iowa State University in Aerospace Engineering. His supervisors for the project "Interactive Visualization of 3D Finite Element Data" were Andrew Johnson (AHPCRC-UM), Shahrouz Aliabadi (AHPCRC-Clark Atlanta University), Tezduyar, and Steve Demlow (AHPCRC-Network Computing Services). The project involved creating a program to view the meshes of various images, and included the creation of 2D data from 3D meshes. In Figure 2, a simplified model of a helicopter with the surface element faces shaded and outlined is shown. The main code was written in C; the GUI was created with Tcl/Tk, and the graphics were done with OpenGl. The mesh generator and flow solver used in this project were developed by the T*AFSM.

Erin Schuster is pursuing a degree from the Massachusetts Institute of Technology in Chemical Engineering. Her supervisors for the project "Mixing During Growth of Single Crystal KDP from Solution: Visualizing Shear Stress" were Andrew Yeckel and Jeffrey Derby (AHPCRC-UM). The objective was to use finite element method to calculate the shear stress exerted on the faces of a potassium dichloride (KDP) single growth crystal spinning in an aqueous KDP
Figure 3. Shear stress on a crystal during acceleration in a solution.
Figure 4. Display of data at various cross-sections from 3D computation of flow past a cylinder. Colors represent the streamwise component of the velocity.
solution. In Figure 3, the shear stress on the crystal during acceleration in the solution is shown. Both the magnitude and the direction of the shear stress on the crystal were factors in the development of defects which could have rendered the final product useless.

Michelle Viera-Vera is pursuing a degree from the University of Puerto Rico, Mayaguez Campus, in Computer Engineering. Her supervisors for the project "Interactive Visualization of 3D Finite Element Data" were Johnson, Aliabadi, Tezduyar, and Demlow. The objective was to develop interactive software in order to view and properly present 3D finite element flow data. Figure 4 shows flow data at various cross-sections from 3D computation of flow past a cylinder. Colors represent the streamwise component of the velocity. The mesh generator and flow solver used in this project were developed by the T*AFSM.

Mark Wibben is pursuing a degree from the University of Minnesota in Aerospace Engineering and Mechanics. His advisors for the project "Parallel Finite Element Simulation of Parachute Applications" were Keith Stein, an Aerospace Engineer at the US Army Natick Research, Development, and Engineering Center (RDEC) and Tezduyar. The objective was to investigate the performance of a flexible, wing-shaped para-glider. Because of the wing's flexibility, it was necessary to consider the fluid-solid interaction in a system consisting of the wing and the surrounding flow field. It was also desirable to determine what effects the inevitable deformation of the wing would have on the performance, namely, the lift-to-drag ratio (L/D).

The project consisted of two parts. The first part involved investigating the effects of flexibility on a wing section. Meshes were generated with different degrees of spanwise curvature and input into a flow solver based on the Navier-Stokes equations. It was shown that L/D decreased with increasing spanwise curvature for a given angle of attack.

The second part of the project involved the creation of a 3D mesh of the entire flexible wing. This mesh was input into the same flow solver as the one used for the previous meshes. The resulting pressure distribution and the geometry of the wing were input into a structural dynamics code, along with material properties, to update the geometry for the wing. This refined geometry was input back into the flow solver. This process was repeated until a single, converged solution was obtained. In this fashion, the performance of the wing was determined. Figure 5 shows the finite element mesh, surface pressure distribution, and streamlines. The mesh generator and flow solver used in this project were developed by the T*AFSM.

Figure 5. Simulation of flow past a semi-rigid, gliding wing. Finite element mesh, surface pressure distribution and streamlines.
Figure 6. Deformation of a parafoil and the air pressure around it.
Johnny Wu is pursuing a degree from The Cooper Union for the Advancement of Science and Art in Civil Engineering. His supervisors for the project "Parallel Finite Element Simulation of Fluid Flow Applications From Mesh Generation to Flow Visualization" were Vinay Kalro (AHPCRC-UM) and Tezduyar. The objective was to simulate the fluid-structure interaction of a parafoil using finite element simulation. Figure 6 shows deformation of the parafoil and the air pressure around it.

A national competition for selecting the interns for the 1998 Summer Undergraduate Internship Program in Fluid Dynamics will conclude in February 1998. Six interns are expected to participate in the Program, which will be held 15 June through 21 August. The 1998 summer projects are listed in Table 1.


Table 1. 1998 Summer Internship Projects.
Interactive Visualization of 3D Finite Element Data
Project Supervisors:
Andrew Johnson, Aerospace Engineering and Mechanics (UM)
Shahrouz Aliabadi, Engineering (CAU)
Tayfun Tezduyar, Aerospace Engineering and Mechanics (UM)

Parachute Fluid–Structure Interactions—Response of Parachutes to Adverse Flow Conditions
Project Supervisors:
Keith Stein, US Army Natick RDEC
Tayfun Tezduyar, Aerospace Engineering and Mechanics (UM)

Simulation of Free Surface Flows in Channels
Project Supervisors:
Marek Behr, Aerospace Engineering and Mechanics (UM)
Tayfun Tezduyar, Aerospace Engineering and Mechanics (UM)

Parallel Computation of Wake Flows Affecting Secondary Objects
Project Supervisors:
Yasuo Osawa, Aerospace Engineering and Mechanics (UM)
Vinay Kalro, Aerospace Engineering and Mechanics (UM)
Tayfun Tezduyar, Aerospace Engineering and Mechanics (UM)

Extraction and Visualization of Data Sets Generated in Complex, 3D Finite Element Flow Simulations
Project Supervisors:
Vinay Kalro, Aerospace Engineering and Mechanics (UM)
Tayfun Tezduyar, Aerospace Engineering and Mechanics (UM)

Finite Element Simulation of Fluid Flows and Moving Structures
Project Supervisors:
Steve Ray, Aerospace Engineering and Mechanics (UM)
Gloria Wren, Army Research Laboratory
Tayfun Tezduyar, Aerospace Engineering and Mechanics (UM)