Calculating Wetted Area of Saab Gripen 39A

[ChrisHarvey]

As part of a piece of coursework, I need to be able to calculate the total wetted area of the Saab Gripen 39A.

Firstly, I have found several conflicting definitions of the term 'wetted area', although I now believe it is the sum of the projected areas from the top and bottom, port and starboard, and front and back views. Is this correct?

Secondly, before I set to work with a general arrangement drawing and start scaling up lengths to calculate areas, etc. is there an analytical way I can do this? I've collected basic data for the Gripen such as Lift coefficient and cruise and stall, drag coefficient at max speed, max. thrust, aspect ratio, wing loading, etc. I'm sure there must be a way to do it using a selection of the data we've been told to find because it clearly says 'calculate', and somehow basic geometry doesn't seem to involve much calculation. Also I can expect large errors doing it geometrically (which ideally I don't want).

Thanks very much,
Chris

 

[zmike]

Hi Chris,

It sounds like you may have the right idea when it comes to wetted area. The sum of the projected areas from the top and bottom, port and starboard, and front and back views is an accurate definition of wetted area.

Unfortunately, calculating wetted area analytically can be rather difficult, as it depends on a variety of factors such as the shape of the aircraft and its surface area. As such, your best bet may be to scale up lengths from the general arrangement drawing and calculate the areas manually. You mentioned that this would be prone to errors, but as long as you're careful and double check your work, you should be able to get an accurate result.

Good luck with your coursework!

 

[ravenprp]

Hi Chris,

To calculate the wetted area of the Saab Gripen 39A, you can use the following formula:

Wetted Area = 2 x (top and bottom projected area) + 2 x (port and starboard projected area) + 2 x (front and back projected area)

The projected areas can be calculated using the wing span, length, and height of the aircraft. You can also use the aspect ratio and wing loading to estimate the wing area.

Another method to calculate the wetted area is by using the drag coefficient and lift coefficient at different speeds. You can use the drag equation (D = 1/2 x density x velocity^2 x drag coefficient x wing area) to calculate the drag force at different speeds. Then, you can use the lift equation (L = 1/2 x density x velocity^2 x lift coefficient x wing area) to calculate the lift force at those speeds. By plotting the drag and lift forces on a graph, you can determine the area under the curves, which represents the wetted area.

I would suggest using both methods to cross-check your results and ensure accuracy. Also, make sure to double check your units to ensure consistency.

I hope this helps. Good luck with your coursework!