Calculation of 'Mean velocity pressure' as per BS EN 1991-1-4 and query

[ambesan2019]

Hi All,

I am calculating 'Reference mean velocity pressure' ( qb ) using Eqn. 4.10 of BS EN 1991-1-4.

I am unsure whether I shall take 'Air density' = 1.25kg/m3 along side vb = 24.46 (which is in 'm/s) while calculating 'Mean velocity pressure' or shall take density of air density in 'kN/m3' . Please note, if I take density of Air in 'kN/m3' then there is a difference of 'one decimal point' ( which is a massive difference'. )




Many thanks for your help in advance.

 

[HTURKAK]

qb=0.5*1.25*(24.46**2)=374 N/m2 = 0.374 kN/m2

If vb=24.46 m/sec , ρ=1.25 k/m3 , the basic velocity pressure will be 0.374 kN/m2 . Your calculation is OK.

 

[Snickster]

F = ma Where mass "m" is in kg mass per newton's law and A is in meters/sec^2

F = m (dV/dt) Acceleration "a" is change in velocity over time

F = (m/dt) dV= (Rho)(A)(V)(dV) where "m/dt" mass/sec = kg/sec = Rho(A)V

F/A = P = (Rho)(V)(dV) Where "P" is pressure = Force/area and "Rho" = density in kg/m^3

Integrate right side:

P = 1/2 (Rho) (V^2)/2