Hydromechanics: Venturi and Coanda Effects

[JEB]

My question primarily relates to an object planing across a fluid surface.

First, does the Venturi effect only apply to enclosed systems such as pipes?

My true motives are to understand the physical forces acting on a surfboard as it travels down and across a wave.

I’m currently in the process of analyzing how water flows across the bottom of a surfboard. This has turned out to be quite complex because water rarely flows directly from nose to tail on the surfboard. A brief introduction to surfboard design may be needed. Generally, boards are designed with some sort of concave on the bottom. The concave is wide where the water contacts the board and gradually narrows until it exits the tail. This gradual restriction is guided by the rails. Some boards use a single to double concave out the back. The boards also have a convex shape because of the rocker.

My question is, can the small amount of channeling invoke the venturi effect? And will the Coanda effect occur similar to a spoon; essentially will the water follow the length of rail out the back of the board?

 

[LightHero]

In short, yes, the Venturi effect and Coanda effect can both apply to the surfboard as it moves through the water. The Venturi effect occurs when water is forced through a narrower passage, and the Coanda effect occurs when a fluid follows the contour of a curved surface. In the case of the surfboard, the concave in the bottom creates a curved surface and the rails create a narrower passage for the water to flow through, thus invoking the Venturi effect. The water will then follow the curved surface of the board, which is known as the Coanda effect.

 

[charng]

I can say that the Venturi effect does not only apply to enclosed systems such as pipes. It can also occur in open systems, such as the flow of water over a surfboard. The Venturi effect is a result of fluid flow being constricted, causing an increase in velocity and a decrease in pressure. This can happen in any situation where there is a change in the cross-sectional area of the flow, which can occur on a surfboard due to its concave shape.

Additionally, the Coanda effect can also play a role in the flow of water over a surfboard. This effect describes how a fluid will follow a curved surface, as seen with the spoon example you mentioned. In the case of a surfboard, the water may follow the length of the rail as it curves towards the back of the board. This can create a pressure difference between the top and bottom of the rail, resulting in lift and stability for the board.

However, it is important to note that the behavior of water flow over a surfboard is complex and can be influenced by many factors. The specific design of the board, as well as the shape and size of the wave, can all affect the hydrodynamics of the board. It may require further analysis and experimentation to fully understand the physical forces at play in this situation.

In conclusion, while the Venturi and Coanda effects may play a role in the flow of water over a surfboard, there are likely other factors at play as well. Further research and analysis may be needed to fully understand the dynamics of this system.