I want to refer to this:
i will describe it shortly
guy uses such forces
Viscous Water Resistance - the force that acts like skin friction drag
Pressure Drag Forces - something that acting towards/outwards the hull center within each surface of the hull model,
guy uses some coefficients that i am unable to find:
FDi = -(CPD1*Vi/Vr + CPD2(Vi/Vr)^2)*SubmergedSurf*(cos(Thetai)^fp * surf_normal, if cos(Thetai)
positive
fp -> falloff power of the facing dot product,
CPD1 - linear pressure drag coeff
CPD2 - quadric pressure drag coeff
FDi = -(CSD1*Vi/Vr + CSD2(Vi/Vr)^2)*SubmergedSurf*(cos(Thetai)^fs * surf_normal, if cos(Thetai),
negative
Same as above but instead of pressure we call them suction forces
cos(thetai) is an angle between velocity and surface normal
i wonder how to determine such coefficients.
Why i cant use here drag equation with a changeable drag coeff depending on fluid velocity + surface velocity multiplied by abs(arccos(cos(thetai))) / pi to get the max value when surface is facing exactly the velocity vector
Slamming Forces - same quaestion as above why i cant just use drag equation for that.
and how to calculate a volume of that shape:
i ask that becasue i have divided hull into 8 boxes that are coevering it and use their center as the hooks for forces to apply,
i divide each box by one plane (they may differ for different boxes) i cant get the image of slicing such model where everything is connected and i have different slice planes for different triangles in the hull.
more over i am not quite sure if guy uses the buoyant force at all) or may he calculates it by looping through surfaces submerged in water and applies a force pointing -surface_normal for each depending on hull vel + fluid veli
i mean depending on how deep a triangle of the hull penetrates the water it has different pressure acting on it along through its shape (lets take a mean of that) so actually pressure of water below that surface pushes it up - i would stand for that, but i dont understand the equation + guy uses Vr which is unknown. (despite 6 other coefficients that are really hard to guess)
so there should be a drag equation for that since P = F / A, its strictly related to the velcotiy of fluid + the hull triangle(surface), and force which could be found by F=ma but theres a problem how do i find a proper mass of water that hit the target, thats way out of scope when i see 1000m^3 of water hitting the boardside, yeah i could do p = m / V => m = p*V (density * volume) but how to find then a volume of it.
more over going back to my simple implementation which acts wierdo on small waves (along with a 'rough water')
theres another thing how do i find water velocity i only have a heightmap that changes i have all vertices calculated for each timestep so i could know the translation along y axis for the water but how to compute x,z velocity from that so i could apply a proper drag for each surface of the hull.
because without it i can only apply drag putting in equation ship velocity and forcing it to act in the opposite direction (of that ships vel) which gives me really bad results.
and last confusion should i add bouyancy force when i calculated pressure acting on each surface (in my understanding that should be the buoyancy force itself)
i wouldn;t even ask how to apply some of forces since i dont even have a mass for each surface...