“Flow over a Cylinder” Report Guidelines – Thermo-Fluids 3 -1-Wind Tunnel Guide 1. Introduction to Experiment There are at least six different ways to find (or estimate) the drag coefficient of a body fully immersed in a moving fluid. These methods are: 1. Direct measurement of the force on the body 2. Finding the loss of momentum of the fluid 3. Potential flow theory 4. Applying empirically derived drag coefficient data from the literature 5. Integrating the surface pressure profile 6. Solving the flow using Computational Fluid Dynamics (CFD) In this report you will be using method 4 (Ansys-CFX) and 5 (wind tunnel) to compute the Cd of the circular cylinder. 2. AIM: To determine the drag coefficient of a circular cylinder by: Obtain Cp (coefficient of pressure) values around the circular pipe. Integrating Cp over the entire cylinder Why do we need to use Cp? Cp describes the relative pressures throughout a flow field. As it is a non-dimensional number, scaled down models can be tested in wind tunnels that represent larger scales whereby pressure coefficients can be determined at critical locations around the model, and these pressure coefficients can be used with confidence to predict the fluid pressure at those critical locations around a full-size models. 3. Description of Experiment The portable small wind tunnel will be used for this experiment (Figures 1 to 4). It has a square test section of nominal size 300 mm×300 mm×500 mm (width, height and length respectively). Flow is drawn through the tunnel by an axial fan located at the tunnel exit (see Figure 2). A circular cylinder with a diameter of 13mm is mounted in the test section. A Pitot-static tube is mounted on a traversing gear that can move vertically up and down to measure the local value of velocity behind the cylinder. The working principle and relevant theory of a Pitot-static tube can be found in any standard fluid mechanics textbooks. The local static and total (stagnation) pressure can be measured…