Author Topic: How to calculate Cd  (Read 5665 times)

mman

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Re: How to calculate Cd
« Reply #15 on: January 08, 2015, 04:21:25 PM »
375CT,

There are lot's of analytical and numerical ways to estimate Cd directly. However the method I just told you is one of the most accurate and still very simple.
If you don't know the actual BC of your bullet use measurements and drawings from Litz's book to estimate form factor and calculate BC from it (I have done this numerous times and usually get the BC right with the accuracy of 3-4 % which is better than I can manage with CFD). All you need for this method is good reference bullet. When you have BC then just use G-drag curve as shown before to calculate Cd.

375CT

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Re: How to calculate Cd
« Reply #16 on: January 09, 2015, 03:11:15 AM »
375CT,

There are lot's of analytical and numerical ways to estimate Cd directly. However the method I just told you is one of the most accurate and still very simple.
If you don't know the actual BC of your bullet use measurements and drawings from Litz's book to estimate form factor and calculate BC from it (I have done this numerous times and usually get the BC right with the accuracy of 3-4 % which is better than I can manage with CFD). All you need for this method is good reference bullet. When you have BC then just use G-drag curve as shown before to calculate Cd.

Mman, thanks again for your kind reply.

Are you aware of any other method, besides McDrag to compute Cd?

mman

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Re: How to calculate Cd
« Reply #17 on: January 09, 2015, 06:55:29 AM »
I can't give you direct references I'm afraid but I have seen some of them along the way. For me those are not very interesting since most are not that accurate except perhaps limited projectile shapes.

Let's see if robert can do a better job with his new project.