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Unformatted text preview: CE 321 INTRODUCTION TO FLUID MECHANICS 2004 LABORATORY 1: FLUID STATICS Objectives: • To experimentally verify the accuracy of the equation derived from hydrostatic theory to predict the location of the center of pressure on a submerged plane surface (Eq. 1) c c xc R y A y I y + = (1) • To determine whether measurement uncertainty appears to explain the inaccuracies that were observed when comparing experimentally determined values of y R with those predicted using Eq. 1. • To comment on the apparent suitability of Eq. 1 for engineering use and its advantage over the experimental approach. Equipment: Hydrostatic pressure apparatus, set of weights, metric ruler, graduated cylinders. Approach: Begin with the hypothesis that Eq. 1 accurately predicts y R and compare these values of y R to values determined experimentally by an independent well accepted method—a method that relies upon only basic, well established principals and experimental measurements. Assuming the hypothesis is true you should find “good agreement” between the two sets of values of y R . If you find poor agreement you must first establish that this failing is not the result of inaccurate experimental measurements before you can conclude that Eq. 1 is at fault. Assume that the apparatus shown in Fig. 1 and the experimental procedure described on the next page provide an acceptable independent method for determining y R . The apparatus is designed so that the only hydrostatic force that will rotate the balance arm is the force F R that acts perpendicular to the end-area of the quadrant at some unknown distance L 2 below the pivot. This force produces a moment that tends to rotate the balance arm clockwise. This moment is equal to the moment produced by the weight W used to prevent the rotation. Knowing W, L 1 , and the force F R it is possible to calculate L 2 and determine y R without using Eq. 1. These experimentally determined values of y R can be compared to values calculated using Eq. 1. If you find good agreement between the two methods for determining y R you are well on your way to a happy outcome. All experimental measurements are subject to some unknown amount of error. When we report measured values we report the value, for example L 1 , and the uncertainty ( ±∆ L 1 ) that we have about the true value of this quantity. We expect the true value to lie within the limits established by L 1 ± ∆ L 1 . Use this idea to determine if observed inaccuracies may be the result of inaccurate measurements. If that is the case there is no basis for rejecting the hypothesis that Eq. 1 is accurate. LAST REVISION: REVISED BY: FALL 2004 Robert Little/Carlos Sanlley Procedure: A. Read the description of the apparatus in the Appendix to these instructions....
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This note was uploaded on 04/19/2010 for the course CE 321 taught by Professor Mantha,p during the Spring '08 term at Michigan State University.
- Spring '08