Matching Items (2)
Description
The flow around a golf ball is studied using direct numerical simulation (DNS). An immersed boundary approach is adopted in which the incompressible Navier-Stokes equations are solved using a fractional step method on a structured, staggered grid in cylindrical coordinates. The boundary conditions on the surface are imposed using momentum forcing in the vicinity of the boundary. The flow solver is parallelized using a domain decomposition strategy and message passing interface (MPI), and exhibits linear scaling on as many as 500 processors. A laminar flow case is presented to verify the formal accuracy of the method. The immersed boundary approach is validated by comparison with computations of the flow over a smooth sphere. Simulations are performed at Reynolds numbers of 2.5 × 104 and 1.1 × 105 based on the diameter of the ball and the freestream speed and using grids comprised of more than 1.14 × 109 points. Flow visualizations reveal the location of separation, as well as the delay of complete detachment. Predictions of the aerodynamic forces at both Reynolds numbers are in reasonable agreement with measurements. Energy spectra of the velocity quantify the dominant frequencies of the flow near separation and in the wake. Time-averaged statistics reveal characteristic physical patterns in the flow as well as local trends within dimples. A mechanism of drag reduction due to the dimples is confirmed, and metrics for dimple optimization are proposed.
ContributorsSmith, Clinton E (Author) / Squires, Kyle D (Thesis advisor) / Balaras, Elias (Committee member) / Herrmann, Marcus (Committee member) / Adrian, Ronald (Committee member) / Stanzione, Daniel C (Committee member) / Calhoun, Ronald (Committee member) / Arizona State University (Publisher)
Created2011
Description
This thesis focused on verifying previous literature and research that has been conducted on different spherical objects. Mainly, verifying literature that examines both how surface roughness contributes to the overall drag and how wake turbulence is affected by different surface roughness. The goal of this project is to be able to capture data that shows that the flow transition from laminar to turbulent occurs at lower Reynolds numbers for a rough spherical object rather than a perfectly smooth sphere. In order to achieve this goal, both force balance testing and hot-wire testing were conducted in the Aero-lab complex in USE170. The force balance was mounted and used in the larger wind tunnel while the hot-wire probe was mounted and used in the smaller wind tunnel. Both of the wind tunnels utilized LABVIEW software in order to collect and convert the qualitative values provided by the testing probes and equipment. The two main types of testing equipment that were used in this project were the force balance and the hot-wire probe. The overall results from the experiment were inconclusive based on the limitations of both the testing probes and the testing facility itself. Overall, the experiment yielded very limited results due to these limitations.
ContributorsMilroy, Maxwell (Author) / Takahashi, Timothy (Thesis director) / Adrian, Ronald (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / W. P. Carey School of Business (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05