# Active and passive drag

1. Apr 25, 2010

### Fairytales

Hello,

I'm a french student. I will have to present a project for an entrance examination in a year's time and I've chosen to work on swimsuit. (is it considered as howework ?)
The problem is that I find most of the information on english writen websites, which makes it hard to understand.

In fact I found that there were 3 types of drag opposing a swimmer : surface drag, form drag (inertial drag) and pressure drag. The problem is that I don't understand in what way active and passive drag are related to these 3 kinds of drag.

2. Apr 25, 2010

### willem2

Passive drag is the drag you get when you tow a swimmer through the water.

Active drag is the additional drag because of swimming movements.

Surface drag, also called skin friction.
this is due to the viscosity (thickness) of the water.
proportional to the speed and to the surface area of the swimmer.
This will be nearly the same for active and passive drag, as the amount of surface will change little when swimming as opposed to floating

Form drag / pressure drag. These are the same. For a swimmer at the surface or a small boat, actually wave making drag is the most important form of drag (It's also called wave drag, but that is something different for aircraft). It will go up a lot when swimming.

see http://en.wikipedia.org/wiki/Wave_making_resistance" [Broken]

Last edited by a moderator: May 4, 2017