EGR 365 Laboratory 1 Introduction to Fluids Lee C Groeneweg Tuesday May 11 1999 Purpose To provide a variety of experiences with fluids which will serve as a basis for future study and future analysis To provide practice in careful observations as related to good experimental method Observations The following are the observations that were made at the various stations of this lab 1 Flow Around A Wing At low speeds the tuft of yarn curled back towards the wing when the wing was set around 4 degrees At higher speeds the tuft curled back when the wing was positioned around 13 degrees At the wing tips a vortex was created from what appears to be the wind coming over the wing and the wind coming from the side of the wing The position of the yarn in relation to the wing affected whether the tuft would be blowing straight or if it would curl back towards the wing High speed was when the manometer read 2 static Low speed was when the manometer read 1 static 2 Flow Visualization When the horseshoe piece was placed in the tank it would create a vortex and flow to each side of the round tube For the cylinder we laid in at an angle to see the flow through it The die flowed along the center axis of the tube with the water diverted to flow in that direction For the square rod in the path of the flow with the face normal to the flow stream The flow would approach the rod but when it cam near it the water would roll upward near the wall of the rod but not touching it Then it would flow around the rod 3 Ping pong Ball Could nest the ball in the cup and spin it We could adjust the ball s velocity by adjusting the amount of airflow around the ball Suspended the ball in the stream of the air The ball would not spin Noticed that the ball was suspended in air but away from the central axis The airflow was affected by our hands placing the ball into the stream as we tried to place the ball in the air stream Once we got the ball to balance in the air stream it would float but if it moved out of the stream it would fall Sometimes it would bounce back into the air stream and float again Putting hand over the ball did not affect the ball floating in the air Any obstruction of the air below would cause the ball to fall 4 Flow Around a Bend Pressure was less in the center Indicated by a higher manometer reading in the middle There was greater pressure at the ends of the bend Partially covering the end of the bend would cause an increase in pressure lower manometer levels This was an increase in the external pressure compared to the internal pressure When partially covering the end of the bend could see the flow of air as shown on our arm hair The deflection of the air by the fingers would result in a different flow of air on the hairs The hair served to see a visual of air and it s motion This was similar to the wind tunnel except that we did not notice any back draft of air 5 Glycerin Tank Turned to cylinder in the middle to see the viscosity difference of the glycerin Noticeably different than water even though they have close to the same density A square shape was made in the glycerin to track the flow as the center cylinder was turned As the cylinder was turned the square began to elongate by forming a tail first This tail then became longer and longer as the cylinder was continually turned Eventually the square formed a trail all the way around the cylinder 6 Rocket Experiment To collect data for this experiment we had to design an apparatus to launch the rocket from A board 13 in length was raised on one side 5 upward This created an angle of the launch pad of 37 94 degrees Actual launch angle was affected by the manual holding of the pump and the rocket prior to launch To get good data a few test flights were done to familiarize oneself with the operation of the rocket Values for the Number of pumps Range values in feet 5 10 15 20 25 30 10 24 33 41 41 45 Graph charting Range values in feet versus Number of pumps is shown blow Number of Pum ps vs Range 50 45 Range feet 40 35 30 Series1 25 20 15 10 5 0 0 5 10 15 20 25 30 Number of Pum ps In the initial test flights it was noticed that the more water in the rocket the greater the pressure would get Fewer pumps would be necessary to create a large pressure inside the rocket when rocket was filled with more water The water would all be expelled during the launch Leading to the theory that the rocket had initial thrust but then entered a free fall state after the initial thrust exhausted Noticing this and getting wet form the rocket thrust we put less water in the rocket on our trails Greater pressure in the rocket led to more inaccurate results due mostly to the errant trajectory of the rocket Development of function relating Range to number of Pumps is attached Unanswered Questions Flow Around a Wing What caused the air to turn back on itself How does the air flow over and under the wing How do you determine the optimal angle for the wing for certain speeds Flow Visualization What caused the vortex too be created when the horseshoe piece was put in the tank does fluid follow a set path when it encounters an obstruction what causes the flow to enter the open a space in the van door simulation What caused the flow to curl up the rod but not touch it when it approached it Ping Pong Ball How does the airflow around the ball hold the ball up What keeps it from spinning When in the cup how does the air get around the ball to cause it to spin Flow Around a Bend Why is the pressure lower in the middle What cause the pressure difference What kind of things does this affect in design considerations Glycerin tank If the density of glycerin and water are the same how is it that their viscosity s are different Why can you draw in glycerin but the same action in water will not work What benefits are there for glycerin over water when needing a substance with similar densities