Converting kN/m2 to either mph or m/s

[ironictwist]

Any ideas? It's driving me effin insane

Want to convert 2.353kN/m2 & 1.5kN/m2 into either to m/s or mph.

Failing that...Convert 80, 100, 150mph into kN/m2.

HELP!

[mcdjl]

Isn't kN/m2 a force? If so that means that it won't translate into a speed unless you know what its pushing (in which case i think you'll actually get the acceleration)?

[ironictwist]

mcdjl said:

Isn't kN/m2 a force? If so that means that it won't translate into a speed unless you know what its pushing (in which case i think you'll actually get the acceleration)?

Indeed...I've got the weight in kg, it's near 1/4 of a ton but I'm trying to calculate the equivalent wind speed for this amount of force hitting a glass balustrade :/

[Sgt Bilko]

I don't think you can do this purely because kN/m2 is a pressure unit and m/s or mph is a velocity unit.

Are you trying to calculate wind force on the glass balustrade?

Edited by Sgt Bilko on Friday 5th June 14:20

[Corpulent Tosser]

ironictwist said:

Any ideas? It's driving me effin insane

Want to convert 2.353kN/m2 & 1.5kN/m2 into either to m/s or mph.

Failing that...Convert 80, 100, 150mph into kN/m2.

HELP!

2.353 Kn/m is equal to 1735.481 lbf/ft or 20825.77 lbf/in

1.5Kn/m is equal to 1106.342 lbf/ft or 13276.1 lbf/ft

These are the conversions to imperial

Kn/m is a unit of torque not speed.

[RDE]

Do you mean you want to work out what wind speed is causing that pressure?

Drag = 0.5 x rho x V^2 x S x Cd

V is the value you're looking for.
S is the area, but you have a pressure, so Drag/S is the pressure value you've obtained.
rho is the density of the air (in the region of 1.2)
However you won't know the coefficient of drag, Cd. And i'm not sure how to estimate it.

So that's where my usefulness (such as it was) ends.

[ironictwist]

RDE said:

Do you mean you want to work out what wind speed is causing that pressure?

Drag = 0.5 x rho x V^2 x S x Cd

V is the value you're looking for.
S is the area, but you have a pressure, so Drag/S is the pressure value you've obtained.
rho is the density of the air (in the region of 1.2)
However you won't know the coefficient of drag, Cd. And i'm not sure how to estimate it.

So that's where my usefulness (such as it was) ends.

If the cd = the area on which the force is focused on...If I said 990mm height x 900mm wide, would that help?

but to answer your 1st question...That's exactly what I'm trying to find.

Edited by ironictwist on Friday 5th June 15:14

[Galileo]

Wind has pressure due to its velocity. This pressure is calculated from the equation Vp = 0.6V², where Vp is the velocity pressure in Pascals (Pa) and V = velocity, in m/s. 0.6 is a constant, derived from the density of the air, at 20°C.

The Pascal is a measure of pressure. Pressure is force per unit area. The metric unit for force is the Newton. Therefore, the metric unit for pressure is Newtons/square meter or Pascal.

I'm sure you can work the rest out for yourself.

HTH

Edited by Galileo on Friday 5th June 16:58

[tonyvid]

Galileo said:

stuff

I'm sure you can work the rest out for yourself.

HTH

I'm sure I couldn't!

[Galileo]

tonyvid said:

Galileo said:

stuff

I'm sure you can work the rest out for yourself.

HTH

I'm sure I couldn't!

Must try harder!!

If Vp = 0.6V² then V= square root of Vp over 0.6

If Vp = 2.353 Kn/m² = 2353 n/m²
then,
V=62.6232 m/s = 140.0841mph

If Vp = 1.500kn/m² = 1500 n/m²
then,
V= 50m/s = 111.8468mph

Thats how I see it. So I'll sit here and wait for the night shift to say otherwise.

Edited by Galileo on Friday 5th June 16:59

[ironictwist]

Galileo said:

tonyvid said:

Galileo said:

stuff

I'm sure you can work the rest out for yourself.

HTH

I'm sure I couldn't!

tonyvid said:

Galileo said:

stuff

I'm sure you can work the rest out for yourself.

HTH

I'm sure I couldn't!

Must try harder!!

If Vp = 0.6V² then V= square root of Vp over 0.6

If Vp = 2.353 Kn/m² = 2353 n/m²
then,
V=62.6232 m/s = 140.0841mph

If Vp = 1.500kn/m² = 1500 n/m²
then,
V= 50m/s = 111.8468mph

Thats how I see it. So I'll sit here and wait for the night shift to say otherwise.

I owe you one ...Google failed me, but PH didn't.

Thanks! I knew I could rely on this place!

[Galileo]

Your welcome. Oh, and the equation given assumes air density at normal altitudes.

[Tom_C76]

Galileo said:

Your welcome. Oh, and the equation given assumes air density at normal altitudes.

It also ignores shape effects, wind drag etc. What the OP needs to find is a copy of British Standard BS6399 part 2 or CP3 Ch V pt 2. I've left mine at work for the weekend unfortunately.

TC

[RDE]

Galileo said:

Wind has pressure due to its velocity. This pressure is calculated from the equation Vp = 0.6V², where Vp is the velocity pressure in Pascals (Pa) and V = velocity, in m/s. 0.6 is a constant, derived from the density of the air, at 20°C.

Duh! And there's me confusing the issue with Cds when all you need is the dynamic pressure. Who cares about the object the pressure is acting on when you're looking for the velocity that's causing it? No wonder I was rubbish at engineering.

[BonzoGuinness]

Those numbers sound decent to me. At its simplest I get 138.64 and 110.69 mph.

Pulling a bluff body Cd of say 1.9 out of my arse suggests 98.53mph and 78.67 mph, based on the reference area you gave us above. I'm probably very very wrong though (too many assumptions - square-ish panel, perpendicular to flow etc). Never have been very good at fluid dynamics, and I'm not long out of a bloody exam on it.

Edited by BonzoGuinness on Friday 5th June 19:47

[tonyvid]

Galileo said:

tonyvid said:

Galileo said:

stuff

I'm sure you can work the rest out for yourself.

HTH

I'm sure I couldn't!

Must try harder!!

If Vp = 0.6V² then V= square root of Vp over 0.6

If Vp = 2.353 Kn/m² = 2353 n/m²
then,
V=62.6232 m/s = 140.0841mph

If Vp = 1.500kn/m² = 1500 n/m²
then,
V= 50m/s = 111.8468mph

Thats how I see it. So I'll sit here and wait for the night shift to say otherwise.

I was just about to say that.....err

[pimpin gimp]

Corpulent Tosser said:

ironictwist said:

Any ideas? It's driving me effin insane

Want to convert 2.353kN/m2 & 1.5kN/m2 into either to m/s or mph.

Failing that...Convert 80, 100, 150mph into kN/m2.

HELP!

2.353 Kn/m is equal to 1735.481 lbf/ft or 20825.77 lbf/in

1.5Kn/m is equal to 1106.342 lbf/ft or 13276.1 lbf/ft

These are the conversions to imperial

Kn/m is a unit of torque not speed.

kN/m is a loading, kN.m or kNm is a torque, like ft.lb's or lb.ft

[pimpin gimp]

Corpulent Tosser said:

ironictwist said:

Any ideas? It's driving me effin insane

Want to convert 2.353kN/m2 & 1.5kN/m2 into either to m/s or mph.

Failing that...Convert 80, 100, 150mph into kN/m2.

HELP!

2.353 Kn/m is equal to 1735.481 lbf/ft or 20825.77 lbf/in

1.5Kn/m is equal to 1106.342 lbf/ft or 13276.1 lbf/ft

These are the conversions to imperial

Kn/m is a unit of torque not speed.

kN/m is a loading, kN.m or kNm is a torque, like ft.lb's or lb.ft

[RDE]

So important it was worth saying twice

[Galileo]

Tom_C76 said:

Galileo said:

Your welcome. Oh, and the equation given assumes air density at normal altitudes.

It also ignores shape effects, wind drag etc. What the OP needs to find is a copy of British Standard BS6399 part 2 or CP3 Ch V pt 2. I've left mine at work for the weekend unfortunately.

TC

It doesn't ignore them, it just doesn't need to know. The OP wanted to know pressure per square metre. Shape and angles will determine how the body reacts to that pressure. Coefficient of drag etc is a study of the body itself not the force being exerted on the body and is very complicated fluid dynamics. What the OP asked for is simple Newtonian Physics.