ITU Fluids Group

LOW NOISE AXIAL FAN (A thesis by Selahattin Doğramacı)

( *Click image for video)

The following figures show the results after 100 hundred iterations and a full turn of the fan.

Cross-section in z-plane

a) Velocity Vector b) Pressure Contours

As can be seen on Figure (a), the flow is entrained in radial direction and a vortex occurs

behind each blade near the connection of hub. Moreover, Figure (b) shows that blades are

exposed to counteracting positive static pressure.

c) Pressure Contours with Streamlines ( *Click image for video)

d) Closer View of the Pressure Contours

On Figure (d) it is obviously seen that there is negative pressure on the back side of the blade.

Moreover, the lowest pressure occurs at the connection of the back side of the blade and the

hub, and there is a uniform pressure distribution on the blade which can be concluded that there

is no stall on the blade.

e) Velocity Magnitude f) z-velocity and Streamlines

Figure (e) shows the velocity magnitude distribution x plane at x=0. Fluid particles get faster

on their way from inlet region to blades and they have their maximum velocities around the blades.

Moreover, after leaving the blades, they slow down as they go to the outlet region. In Figure (f), z

component of velocity of the fluid particles are displayed. It can be concluded from the figure

that as fluid enters blades, particles are scattered towards the wall due to the centrifugal force.

Moreover, because of this centrifugal effect, they become faster and faster as they get closer to

the wall.

Pressure Distribution on Blades

g) Blowing Side h) Suction Side

Figures (g) and (h) shows the pressure distribution on the front and back surfaces of blades.

As can be seen on the figures, on the front side, pressure is rising from hub to the tips of the

blades, while there is negative pressure on the back side of the blade surfaces.