The desired airfoil for a wind propeller must have a low Reynolds number
(since it depends on the wind speed), and ideally, a very thin but rigid blade.
The free stream velocity, U was fixed at 156 mm/s as the Reynolds number
was about 6250 depending on the diameter of permeable cylinder.
This regime can be characterized by the Reynolds number
, which can be defined as follows :
Figures 9(a) and 9(b) present the variations of the Nusselt number ratio (Nu/[Nu.sub.0]) with the Reynolds number
for the heat exchanger tube inserted with the V-Downstream and V-Upstream wavy surfaces, respectively.
However, these cannot be modified by the user, airfoil selection is limited to a given list, and airfoil aerodynamic data in the low Reynolds number
range are less reliable.
The channel Reynolds number
Re in this work is defined as
The whole study is split into two main parts, one concerned with low- to moderate-Reynolds number cases, 1 [less than or equal to] Re [less than or equal to] 500, and that with relatively high value of Reynolds number
, 500 < Re [less than or equal to] 1,300.
The diameter = 2 mm, Reynolds number
=100, and sheet position = 2 mm.
The flow attack angles of the wavy plate ([alpha] = 15[degrees], 20[degrees], 25[degrees], 30[degrees], 35[degrees], 40[degrees], 45[degrees], 50[degrees], 55[degrees], and 60[degrees]) are varied for the Reynolds number
in the range of 3000-10,000.
We decided to record video segments of the flow at several different Reynolds numbers
. Also, we wanted to display the Reynolds number
for each corresponding flow condition.
It is worth to understand that at low Reynolds number
, the buoyancy strength can significantly muddle the flow field around the confined obstacle.
Figure (4) demonstrate the variation of Nusselt number versus Reynolds number
at different values.