I'm currently working on a project looking at possible commercial uses for open flow marine current turbines (MCT). Although I'm familiar with fluid mechanics, some of the specific aspects of the MCT are new to me and I was wondering whether any people here could help. this is a theoretical investigation so I do not have experimental data.
i) Cut-in speed of a turbine. So far I've had a lot of problems finding information on how to theoretically calculate the speed at which a turbine will self-start.
ii) Speed of flow as it passes through turbines. I've come across a few different methods for calculating this value, but all involve more figures than I currently have. I have the speed of the flow prior to passing through the turbine and the speed that the blades are rotating but I do not have the speed of the flow downstream of the turbine, or the reduction in head. Without either of these values I have been unable to progress with this aspect.
iii) Chord Reynolds number. My results for this seem very high. It may be easiest just to show the data I've used;
c = (S*D)/N
where
c = chord length
S = solidity = 0.25
D = rotor diameter = 12m
N = no. of blades = 3
c = 1m
----------------------------------------------------------
w = (T*U)/r
w = angular velocity
T = tip speed ratio = 3
U = speed of flow = 1.808 m/s
r = radius = 6m
w = 0.904 rad/s
-----------------------------------------------------------
Re = (w*r)*c/v
Re = chord Reynolds number
v = kinemtatic viscosity = 1.4x10^-6
Re = 3 874 000
I was expecting a value of several hundred thousand.
Sorry for the long post, but any help would be appreciated.
