EP-707 Using Quad Energy Savings Calculator

Revision for “EP-707 Using Quad Energy Savings Calculator” created on November 30, 2015 @ 19:29:08

EP-707 Using Quad Energy Savings Calculator
Date: <strong>July , 2015</strong> <h1><strong>1. </strong><strong>PURPOSE</strong><strong> / DESCRIPTION</strong></h1> <ul> <li>To give a guideline on how to use the energy savings and predicted terminal velocity calculator for quads (Excel file) at different angles. <ul> <li>This is useful if you have followed the EPs and ETPs for running wind tunnel simulations on desired bodies. <strong>This procedure will follow an example with the BIONX drone simulations</strong>.</li> <li>This procedure does assume you have decent knowledge of Excel.</li> </ul> </li> <li>File name = “Quad Simulation Data and Calculator” (The calculator itself has comments to guide usage.)</li> </ul> <h1><strong>2. </strong><strong>General Layout</strong></h1> <ul> <li>General Layout</li> </ul> <a href="http://wiki.vairdo.com/wp-content/uploads/2015/11/707-01.png"><img class="alignnone wp-image-492 size-full" src="http://wiki.vairdo.com/wp-content/uploads/2015/11/707-01.png" alt="707-01" width="1267" height="834" /></a> &nbsp; <ul> <li>Inputs <ul> <li>Bolded are values that you will usually change</li> </ul> </li> </ul> <table> <tbody> <tr> <td width="109">Name</td> <td width="72">Units</td> <td width="234">Definition</td> <td width="271">Notes</td> </tr> <tr> <td width="109">Weight</td> <td width="72">N</td> <td width="234">weight of craft including the wing</td> <td width="271"></td> </tr> <tr> <td width="109"><strong>Cl (wings)</strong></td> <td width="72"></td> <td width="234">wing’s coefficient of lift</td> <td width="271">It may be best to do a separate 3D simulation of the wing to obtain accurate Cl and Cd values.</td> </tr> <tr> <td width="109"><strong>Cd (wings)</strong></td> <td width="72"></td> <td width="234">wing’s coefficient of drag</td> <td width="271"></td> </tr> <tr> <td width="109"><strong>Wing Chord</strong></td> <td width="72">m</td> <td width="234">wing chord length</td> <td width="271">Input average chord length if the wing is not rectangular.</td> </tr> <tr> <td width="109"><strong>Wing Span</strong></td> <td width="72">m</td> <td width="234">wing span</td> <td width="271"></td> </tr> <tr> <td width="109"><strong>Wing Area</strong></td> <td width="72">m<sup>2</sup></td> <td width="234">wing planform area</td> <td width="271">For rectangular wings it uses span*area formula, but <strong>for non-rectangular, you must input a flat calculated value for the planform area</strong>.</td> </tr> <tr> <td width="109">Drone Ref Area</td> <td width="72">m<sup>2</sup></td> <td width="234">drone reference area</td> <td width="271">This is the area input in Fluent’s Reference Values section used to calculate Cd and Cl values for the body. <strong>If you used symmetry for simulation, make sure to double that area for this input</strong>.</td> </tr> <tr> <td width="109">Air density</td> <td width="72">kg/m<sup>3</sup></td> <td width="234">density of air at 288.16 °C</td> <td width="271"></td> </tr> <tr> <td width="109">Air viscosity</td> <td width="72">kg/(m*s)</td> <td width="234">dynamic viscosity of air at 288.16 °C</td> <td width="271"></td> </tr> <tr> <td width="109">Area Ratio</td> <td width="72"></td> <td width="234">Wing Area / Drone Ref Area</td> <td width="271"></td> </tr> </tbody> </table> &nbsp; <ul> <li>Craft Cd and Cl <ul> <li>These values should can be found by running simulations on just the body without the wing at varying angles of attack.</li> <li>The example calculated uses results from simulations on the BIONX body, as shown below:<a href="http://wiki.vairdo.com/wp-content/uploads/2015/11/707-02.png"><img class="alignnone wp-image-493 size-full" src="http://wiki.vairdo.com/wp-content/uploads/2015/11/707-02.png" alt="707-02" width="1597" height="735" /></a></li> <li>By creating best fit curves onto the obtained coefficients, you can use them as formulas to interpolate from 0 to 90 degrees in the table. So you will have to change the formula of the cells under Craft Cl and Craft Cd to fit the model. <ul> <li>Make sure to have enough digits in the formula’s coefficients, as by default excel will provide few enough digits to give completely different numbers.</li> </ul> </li> </ul> </li> </ul> <h1><strong>3. </strong><strong>Steps</strong></h1> <ul> <li>Run simulation on the desired wing through fluent or obtain experimental data to find accurate wing Cl and Cd values.</li> <li>Run simulations on the quad body at different angles of attack (check out EP-702,703,705) <ul> <li>Obtain Cd and Cl on the body, make sure to keep the reference area is constant throughout the various angles.</li> <li>If you use symmetry for the simulation, make sure to double the reference area for the Drone Ref Area input.</li> <li>Plot the coefficients against angle of attack, fit a line or a curve on the plots, and obtain the equation. Make sure to have a sufficient number of decimal digits within the equation.</li> </ul> </li> <li>Input all information gathered <ul> <li>Change the formula of Craft Cd and Craft Cl to match what you have obtained from your simulation results. (The coefficients can be constant as well: just make sure to input a constant value for all cells in those columns.)</li> <li>Look to the right of the inputs to see the minimum energy ratio, the required thrust, the angle for that ratio, the terminal velocity, and required velocities for Re # 50,000 and 100,000.</li> </ul> </li> <li>Check that column Vt (m/s) is equal to column Vt (w/Cl). <ul> <li>Vt (m/s) is calculated using combined Cd from the chart while Vt (w/Cl) is calculated using the combined Cl from the chart. If these values do not match, you may have made an error putting in the formulas or values.</li> </ul> </li> </ul>

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