#Turbulent vs laminar flow free

There has been much research done on mach level aircraft where very small ridges are run the width of a wing to prevent turbulent flow, just the opposite that water-cooling enthusiasts seek. Channels with smooth walls and ridges that run parallel to the walls will tend to smooth out the flow and can take turbulent flow and turn it laminar. It could be something as simple as a rougher surface or small ridges that stir up the flow.Ĭare has to be taken to not introduce anything that could contribute to laminar flow.

To add turbulators at the flow entrance and/or along the entire flow length.Ī turbulator would be anything that helps to induce turbulence into the flow.In order to maximize the heat transfer, turbulent flow must be induced as soon as possible into the flow – the entrance length must be minimized.

There are several factors that determine whether a flow will be turbulent or not: channel size and shape, velocity of the fluid, physical attributes of the fluid, etc. There have been several studies that show that for the same net flow of fluid through a channel, a turbulent flow can transfer as much as 150-500% more heat. This results in the entire turbulent flow having a total average higher temperature than a laminar flow. The higher the temperature differential is between two adjacent molecules, the more heat that is transferred between them. Thus the molecules are gaining heat from the hotter source (right next to the water block) rather than from the cooler layers of the flow. In turbulent flow, the molecules are getting tossed and turned all over, with a much great number of the molecules coming in contact or near contact with the water block wall. In laminar flow (remember, nice layers of moving fluid) the heat is conducted through each layer of moving fluid with the inner layers receiving the least (if any) heat transferred into them. If you recall from my previous article, convection in a water block takes place when heat is conducted from the solid water block into the closest molecules of water in the flow. So why do we care about turbulent flow? Because if the flow is turbulent, the heat transferred from the water block (and thus from the CPU) is greatly increased. Why Turbulent Flow is good for Heat Transfer However, in turbulent flow the random action of the water molecules breaks up the boundary layer and disperses the majority of it, thus increasing the ability of all the water molecules to pick up heat from the water block wall. This is especially true of laminar flow because the boundary layer is very thick and, in channels that are small enough, the boundary layer may extend through the entire flow. The problem with having a boundary layer for heat transfer in a water block is that it is actually insulating the inner most layers of flow from being able to pick up the heat from the water block. No matter the case, there will always be some kind of boundary layer.

#Turbulent vs laminar flow free

As the distance from the wall increases, the molecules pick up speed until they are far enough away that the flow feels no effects from the wall this is called the free stream velocity. The molecules of water that are closest to and touching the water block wall are not moving at all, but are stationary. What this basically means is that the boundary layer is the part of the moving water that is feeling the friction or the ‘drag’ of the wall. The boundary layer is defined as the area of the flow that has shear stress forces induced by the solid wall of the water block.