Calculation of dynamic pressure, inertia and drag forces for offshore riser

[Chrissy123]

Hi - I'm trying to calculate dynamic pressure, inertia and drag forces for an offshore riser that is connected to a submersible at the SWL. I have all the data that I think I need, wave period, length, amplitude,height, and I have calculated wave number (k) and wave speed (celerity) s..The depth of the water is 1000m and I want to calculate the dyn pressure, and forces at intervals of 5m down to the bottom of the depth. So I know that z wil be -5,-10,-15 etc ....I am using the equations below P = dynamic pressure, u for horizontal velocity, u dot for acceleration. I know that I have have to calculate the velocity and acceleration as these will feed into the Morisons equations which I'm going to use for inertia and drag forces. My question is what do I use for x and t as these are my unknowns in the equations. Is it ok to assume that at t=0 x= 0 therefore the cos part of the equations go to 1 ? I would be grateful for any pointer please ?

thanks,

 

[Chrissy123]

Actually I know the answer to this now - I'm told in the question that the offset of the riser is 25m in 100s therefore this is my x and t because at t = 100s x = 25m - solved !

 

[MMM]

You have to design by both static and dynamic. The main problem of the dynamic for riser is the vortex induced vibration (VIV) which depend on many factors such as the pipe diameter and the length of the pipe which is the distance between two clamps. For startc as usual calculation drag and inertia force. The dynamic calculation ispresented in this book with free excel sheet for calculation. Marine structure calculation