A comparison and design guide to low-speed contractions, like you need, can be found in one of my papers:

Doolan CJ. Numerical Evaluation of Contemporary Low-Speed Wind Tunnel Contraction Designs. J. Fluids Eng.. 2007;129(9):1241-1244. doi:10.1115/1.2771578.

We also did some work on optimisation of the shape:

http://arc.aiaa.org/doi/abs/10.2514/6.2007-3827

Hope this helps.

A quick response which may be some use (or maybe not). There are some old papers which give design rules for wind tunnel contraction sections which you may find useful. Details are:

Mehta, R D and Bradshaw P (1979) Technical notes: Design rules for small low speed wind tunnels, the Aeronautical Journal of the Royal Aeronautical Society, vol. 83 pp442-449

Pankhurst, R C and Holder DW (1965) Wind Tunnel Technique: An account of experimental methods in low and high-speed wind tunnels, Pitman Press, Bath

Depending on what level of sophistication you want to go to with the uniformity measurements (e.g. mean flow or turbulence intensity) you could just use a pitot-tube to measure the velocity distribution.

I did not get your question completely. But, in general, a uniform flow is the flow that there is no change in flow sparial parameters. As long as you're dealing with a nozzle the uniform flow definition has been violated!

I agree with Mr. Poole's answer, the problem of a uniform jet is a small scale version of a wind tunnel and the same criteria apply. Normally you have a flow rectifier (honeycomb and a series of meshes) and then a contraction as described in the paper of Mehta). Yo do need a HIGH Reynolds number in order not to have viscosity modifying your velocity profile inside the contraction. Even though the Re is high you will not have turbulence unless you let the boundary layer develop (so you need a low boundary layer Re_x but a high Re_D). Measuring with a pitot tube is fine if you have a good pressure measuring sistem. A better measurement would be thermal anemometry but then you need the equipment (I have built a home-made version which works fine) or a LDA. Depending on your budget and on how important the measurement is.

Yet, when the jet impacts with the surface the velocity field will no longer be uniform!!

its true that you can apply the knowledge of wind tunnel design to your particular problem..also keep in mid the contraction ratio....if its too high then most of the flow will simply pass through the middle and you will be left with large recirculating regions......i suggest that you make an initial design and work from there onwards....if you have time you can even do CFD and check various design configurations...the shape of the nozzle (area ratio kept constant) strongly influences the flow given

A comparison and design guide to low-speed contractions, like you need, can be found in one of my papers:

Doolan CJ. Numerical Evaluation of Contemporary Low-Speed Wind Tunnel Contraction Designs. J. Fluids Eng.. 2007;129(9):1241-1244. doi:10.1115/1.2771578.

We also did some work on optimisation of the shape:

http://arc.aiaa.org/doi/abs/10.2514/6.2007-3827

Hope this helps.

A detailed procedure for design of low-speed contractions can be found in one of my papers: Design and Construction of Small Axisymmetric Contractions Part A: Design and Part B: Construction, avaliable in ReserchGate

This is a NOT WELL POSED PROBLEM and can only be solved by LOGIC design of GEOMETRICAL KEYS, like the use of SPLITTER PLATES in the FAR field and AREA RULING near the BODY.

These answers are all well and good, but probably too complicated for you. The easiest route (if you can) is to use a screen that provides a pressure drop maybe 5 times the dynamic head. In that case the gas behind the screen forms a manifold and automatically distributes itself across the screen to give a uniform flow and you don't have to worry about a nozzle. You just have to allow enough distance downstream for the screen generated turbulence to dissipate. You are operating just above 1 atm - not sure what your gas source is - fan? gas bottle?

Also, best to evaluate your techniques based on your goal. Lots of effects going on with 1 atm evaporative coatings. Boundary layers, cross diffusion, etc.

Dear Andrew,

My experience is with heat flux burners to measure the 1D adiabatic burning velocity of a gaseous fuel. In that case you want a uniform outflow from a pipe as well. What we do is taking a perforated plate at the outflow. Below that there is a plenum with a fast converging region to the final diameter! If you want to know more search for heat flux burner on the web.

Cheers, Rob.

Here a link: http://cms.heatfluxburner.org/

http://cms.heatfluxburner.org/

I guess you are looking for the settling chamberpart of a wind tunnel. In the settling chamber, there will be flow straightening devices, such as Honeycombs and Screens. I was working on a reconstruction of a settling chamber at university to meet Rolls Royce requirements for transonic flow. During the research period, it turned out that there is very little information available.

Trust me its complex to attain perfection of flow you are desiring. God's nature is not that easy to simulate and then execute! will reply details later. Regards

Be carefull at low velocities

Thank you everyone for your answers. They have been most helpful in getting me started in this area!

You can use flat plate embedded inside nozzle. additionally, extrude the outlet section of nozzle in order to arrange exited flow and deny from further turbulence.