Shooting Range

[walz]

I have an indoor shooting range of 300 meters length, 35.6 meters wide and 5.0 meters high to be conditioned. I have seen many guides which say that the flow inside the range has to be laminar. Moreover they say that in order to achive the laminar flow, the air velocity should not exceed 0.25m/s. I dont have any proof of this velocity. Equation for laminar flow says that velocity is inversly proportional to the cross-sectional area of air-flow channel. When i computed the required velocity based on the dimensions given above, the velocity calculates out to be 5 FPM only (0.025 m/s). So my questions are

1. How can we determine the velocity of air for a laminar flow in a given size of duct. (In this case i have considered the entire range as a duct of W x H of 35.6m x 5m)
2. Is it required to have laminar flow inside the rnage or is it required to have 0.25 m/s of air velocity inside, or both.
3. Or may be it is required to just throw the air from laminar flow air terminals like Price Laminar flow range.??

any guidance much appreciated.

thanks

Walz

 

[willard3]

Sounds like homework to me.

 

[IRstuff]

His profile indicates otherwise.

I've seen guides that say you need Reynolds number less than 3600, so you might add that to your hopper of answers.

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[berkshire]

I have never done a range that long indoors, 75 feet is the longest I have done.
The requirements at the time were that all air travel from the Shooting position to the bullet stop, and that there be no high velocity air currents anywhere in the bullet travel area.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[imok2]

TRY THISfor information:

http://www.shooting-academy.com/300METER1.html

 

[IRstuff]

What type of weapons are going to be used? For a "standard" NATO 7.62-mm M80 round at 869-m/s muzzle velocity, the tables for 300-m target range show a deflection of 51.5 mm/(m/s), i.e., a 1 m/s crosswind will deflect the round by more than 2 inches at 300 m, which is rather gigantic.

If deflection is limited to 1 mm, then the maximum crosswind must be less than 0.0194 m/s.

So, my take on this is that laminar is not absolutely required, but crosscurrents must be less than 0.019 m/s, IF 7.62-mm M80 weapons are used. Slower ammo would require even lower crosswind.

N.B. It's unclear whether 1-mm deflection might be too extreme. My tables show superelevation in tenths of mils, which would be about 1 inch at 300 m. If you then assume that angles corrections are only accurate to 0.05 mils, and if your wind deflection is less than 1/2 of that, then you could tolerate crosswinds up to 0.15 m/s.

Note that typically, this type of calculation is for a steady crosswind, but the argument would be that if you keep the air flow in general to less than the crosswind limit, you will not significantly affect the accuracy of any of the shooters. I'm guessing that's what the requirement is all about, but it seems to make some sense.

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[GMcD]

This topic came up a little while ago- see this thread:

http://www.eng-tips.com/viewthread.cfm?qid=257304&page=4

Just do a Google search- there are lots of design resources out there. The key is to design so you have between 50-60 feet per minute downrange velocity with a low velocity uniform air supply behind the shooting positions. About 2/3 of the exhaust gets sucked up off the bullet trap, while the other 1/3 should be about 3-4 meters downstream of the shooting position to clear the gunsmoke. All very low velocity terminals.

The key is the bullet trap - make sure the Client is using the Savage Scroll trap- they generate a tenth of the particulates that the old style conventional "smash traps" do. There are other types of bullet traps out there ranging from an angled sand bed, to granulated old rubber tires in a frame assembly. The trap has to make it easy to salvage the lead and copper from the expended rounds.

 

[chicopee]

A laminar flow inside of a shooting range with all these baffles,partitioned cubicles,reeling targets etc... I doubt it that you could achieve that. With air I would expect more of a transition or tubulent flow.