Device and method for measuring the viscosity of a fluid

1. A method of measuring the viscosity of a fluid, the method comprising the following steps:

a) establishing a flow of said fluid under laminar conditions inside a channel ( 14 , 24 ) having a longitudinal direction and an opening with a dimension D, which is transverse to the longitudinal direction, an elongate element ( 12 , 22 ) having a transverse dimension d corresponding to a greatest dimension in a cross section thereof, being placed in said channel substantially along the longitudinal direction thereof and substantially at a center thereof and along the dimension D, a fraction l of the length of the elongate element being immersed in said channel, the ratio D/d being greater than 5;

b) measuring the friction force (f) exerted by said fluid on the walls of said elongate element;

c) calculating the dynamic viscosity (TO of said fluid using the following equation:

f=ληlU   (1)

where:

U is the mean speed of the flow; and

λ is a geometrical factor, and wherein steps b) and c) are implemented in succession for different positions of said elongate element in said channel, along the characteristic transverse dimension D.

2. A method according to claim 1 , wherein steps a) to c) are implemented for a single value of U, when the fluid is newtonian.

3. A method according to claim 1 , wherein steps a) to c) are implemented successively using different values of U, when the fluid is non-newtonian.

4. A method according to claim 1 , wherein said method is implemented continuously.

5. A viscosity meter implementing the measurement method according to claim 1 , and comprising:

a channel ( 14 , 24 ) having a longitudinal direction, a length L and an opening with a dimension D, the dimension D being transverse to the longitudinal direction;

an elongate element ( 12 , 22 ) having a transverse dimension d corresponding to a greatest dimension in a cross section thereof, and having an immersed fraction of length l, the ratio D/d being greater than 5, said element being placed in said channel in such a manner as to extend substantially along the longitudinal direction of said channel, substantially at a center of the channel along the dimension D;

measurement means ( 13 , 23 ) for measuring the friction force (f) exerted on the walls of said elongate element when a fluid flow is established in said channel and circulates through the opening of said channel and along the length of said channel, and

means for moving the elongate element in translation in the opening of the channel in order to measure variations in the friction force with the position of said element along the transverse dimension.

6. A viscosity meter according to claim 5 , associated with means for causing the fluid to circulate, said means comprising an imposed flow rate pump.

7. A viscosity meter according to claim 6 , wherein said channel ( 14 ) is defined by the empty space between two substantially parallel plates ( 10 , 11 ).

8. A viscosity meter according to claim 6 , wherein said channel ( 24 ) is defined by a cylindrical vessel ( 20 ).

9. A viscosity meter according to claim 6 , wherein the channel and the elongate element are elements for single use.

10. A viscosity meter according to claim 5 , wherein said channel ( 14 ) is defined by the empty space between two substantially parallel plates ( 10 , 11 ).

11. A viscosity meter according to claim 10 , wherein the channel and the elongate element are elements for single use.

12. A viscosity meter according to claim 5 , wherein said channel ( 24 ) is defined by a cylindrical vessel ( 20 ).

13. A viscosity meter according to claim 12 , wherein the channel and the elongate element are elements for single use.

14. A viscosity meter according to claim 5 , wherein the channel and the elongate element are elements for single use.