Flow Visualization in a Water Channel - Fluid Flow - Lab Precalculations, Study notes of Fluid Dynamics

Download Flow Visualization in a Water Channel - Fluid Flow - Lab Precalculations and more Study notes Fluid Dynamics in PDF only on Docsity! Precalculations A. Laser Velocimeter (10) 1. In this lab, freestream velocity will be measured with a laser velocimetry (LV) system (also called a laser Doppler velocimetry (LDV) system. The main advantage of this technique is that there is no probe of any kind to disturb the flow – only laser beams enter the flow field. Using the listed references as needed (or some other reference if preferred), provide in the space below a brief description (including sketches) of how a laser velocimeter system works. docsity.com (4) 2. The LV system used in this lab is a fiber optic system, which enables some of the optical components (such as the focusing lens and the photodetector) to be permanently mounted on a portable probe. The probe is in turn mounted on a traversing system so that it can be easily moved around to measure velocity in different parts of the flow field. In the space below, list some other advantages of a fiber optic LV system, as compared to a standard optical LV system: B. Reynolds number considerations (2) 1. Water at room temperature has a kinematic viscosity of  = 1  10-6 m2/s. As mentioned above, the maximum freestream speed of our facility is around 1.3 m/s. With these fixed parameters, estimate the diameter of a smooth sphere required to observe a “drag crisis”. Hint: from Figure 1 of the Background section, a Reynolds number Red = Vd/ of around 4  105 is required. Show all your work in the space below: drequired = inches (1) 2. Is this feasible in our water channel, where the test section is only 6  6 inches square in cross section? Clearly, we can not observe a natural drag crisis on a smooth sphere in our water channel. Let us now examine whether we may be able to observe the drag crisis on a golf ball, which has a very rough surface. (3) 3. Using the published data of Figure 1, the known maximum speed of our water channel (1.3 m/s), and the known diameter of a golf ball (d = 1.68 inches), will you be able to observe the drag crisis on a golf ball in our water channel? Show all your work in the space below: docsity.com