Mecaflux proposed in the tab drag force and lift force of Profiles and airfoils A set of database objects for which the parameters of drag are included. You can quickly assess the drag force of the object in a fluid of your choice by entering the dimensions in the diagram.

The running resistance of a boat hull requires testing basins and software assisted hydrodynamic calculations of powerful computers.

In hydrodynamics Naval sometimes used a method, the method of dual models. It involves deep immersion in tow form, composed of the model hull of a ship and its symmetry to the waterline. The measured drag is then divided by two. The profiles drag (Cd) is already set in Mecaflux thus serve to evaluate the resistance hydrodynamics viscous.

But we can still evaluate "an order of magnitude" for the drag force with MECAFLUX if we're not too greedy precision. The simplest method is to select a geometric object that is closest to a hull of the boat and with our data set:

Suppose we need an order of magnitude of the resistance force of a hull boat 10m long by 2m wide by 1m deep for a velocity of 10 knots.

1-We can use an ellipsoid 10m x 2m and divided by 2, drag found: half ellipsoid similar to our hull. (This method does not take into account surface effects)

select-ellipse profiles with drag

-Enter a length of 10 meters

-Enter a diameter of 2 meters

 

We estimate our resistance to progress from the ellipsoid and the place around 2100 Newtons (excluding resistance wave

The results are:

4157Newtons (424 Kg.f) divided by 2 = 2078Newtons (212 Kg.f) is 213 kilogram-force resistance force or drag for a vessel of 10 meters by 2 meters wide, 1 meter deep at a velocity of 10 knots

Exemple External flow drag and lift