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In preparation for a Fluid Mechanics experiment, I am looking for a simple commercial ready made apparatus to generate a linear velocity trend to prove a new theory:

https://aip.scitation.org/doi/abs/10.1063/1.4964761

The load is around 10kg starting from rest to reach linearly say a 0.5m/sec within a distance of say 0.5m.. Any hints ? :)

72nd Annual Meeting of the APS Division of Fluid Dynamics Volume 64, Number 13

The Leading Edge theory: a new insight into the laminar Boundary Layer by Mohammad Gabr

The Abstract :

The flow properties at the leading edge of a flat plate represent a singularity to the Blasius laminar boundary layer equations; by applying the diffusion equation where the velocity of a moving flat plate in a stationary fluid is diffused to the far field, the leading edge velocity profiles are studied. Experimental observations as well as the theoretical analysis show an exact Gaussian distribution curve as the original starting profile of the laminar flow.To conclude; the main key results are as follows: [1] The velocity profiles at the leading edge of a flat plate are Gaussian Curves that grow in space and time; whereas the Blasius velocity profile is a part of the general Gaussian curves solution. [2]A new method to calculate the friction drag is successfully tested, based on the displacement area of the leading edge velocity profile. [3] In order to obtain the final physical proof of the new theory it is recommended to carry out experiments using an ultra-thin flat plate moving in a stationary fluid and measuring the velocity profiles at the leading edge with different measurement techniques.

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  • $\begingroup$ Welcome to engineering.SE! If the new theory for your experiment matters for the question, you should briefly summarize it in the text, since the link might at some point in the future get outdated. $\endgroup$
    – OpticalResonator
    Commented Apr 24, 2020 at 20:16
  • $\begingroup$ Thank you for the advice ... well the link I believe is permanent as long as the AIP .. American Institute Of Physics Journals are permanent .. $\endgroup$
    – M Gabr
    Commented Apr 30, 2020 at 10:19
  • $\begingroup$ The AIP is likely permanent, the link might still change..my bank already changed the URL of their online banking twice, making my bookmarks invalid. Just a suggestion, it could improve the quality of your question and attract more helpful answers. $\endgroup$
    – OpticalResonator
    Commented Apr 30, 2020 at 10:28
  • $\begingroup$ Please edit the question to add the info, don't write it into the comments $\endgroup$
    – OpticalResonator
    Commented May 1, 2020 at 23:56
  • $\begingroup$ Why don‘t you buy a linear drive that has a Position /speed controller...they can be purchased or made readily. $\endgroup$
    – DrMrstheMonarch
    Commented Sep 30, 2020 at 7:15

2 Answers 2

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You could use some sort of rack and pinion (automotive maybe?)with a drive wheel on your pinion shaft... or attach an arm like a bike pedal to move it back and forth, the longer you make the arm the easier to pull but you must pull the longer distance. The theory your testing doesn't affect the question.

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  • $\begingroup$ Well, thank you, but I do need a linear velocity over time trend in a specific way.. to compute the drag force, and I need to have the actual force exerted to compare it with the calculated .. actually, after a long search in the web, I was really surprised that such a simple equipment does not exist ..I wish i am mistaken .... $\endgroup$
    – M Gabr
    Commented Apr 27, 2020 at 0:40
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    $\begingroup$ Yes, I do not know what you would want to use for your control mechanism. A motor that you control the speed of with voltage seems the easiest to make. $\endgroup$
    – Ryan Griffith
    Commented Apr 27, 2020 at 2:33
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Unfortunately the article did not seem to include its experimental procedures. My understanding from your description and comments is that you would like the plate to move at constant velocity of 0.5m/s. And you would like to measure the drag on the plate that may be up to 10kg*9.81m/s^2 = 98.1N.

The best way to do this would to be use a pre-built linear actuator driven by a stepper motor, and powered by a stepper motor driver. The speed of a stepper motor can be controlled directly using a 3D printer control board, a stepper motor tester, or other professional controllers. You will need to make your linear actuator selection based on the the speed, stroke and force needed. I do not recommend using a DC motor because the velocity will depend on the force and will make the experiment difficult to preform.

On this linear actuator you would mount a cantilever or compression type load cell. This load cell would be run back to the appropriate electronics including a load cell amplifier and a method of recording the data such as an Arduino or a DAQ Data Acquisition unit.

From the load cell you could mount a rod that will go through a shaft seal into the tank to attach to the plate. Remember to account for the friction of the seal. You may be able to get creative an do it from the top, but you will have to account for the friction of the supporting members and it may be difficult to hold it parallel to the direction of movement.

As I am answering I noticed the question is dated a few years. How did you end up doing it?

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