Weber number - wikipedia Weber number A splash after half a brick hits the water ; the image is about half a meter across. Note the freely moving airborne water droplets, a phenomenon typical of high Reynolds number flows ; the intricate non-spherical shapes of the droplets show that the Weber number is high. Also note the entrained bubbles in the body of the water, and an expanding ring of disturbance propagating away from the impact site. The Weber number ( We ) is a dimensionless number in fluid mechanics that is often useful in analysing fluid flows where there is an interface between two different fluids, especially for multiphase flows with strongly curved surfaces. It is named after Moritz Weber ( 1871 -- 1951 ). It can be thought of as a measure of the relative importance of the fluid 's inertia compared to its surface tension. The quantity is useful in analyzing thin film flows and the formation of droplets and bubbles. Contents 1 Mathematical expression 2 Applications 3 References 4 Further reading Mathematical expression The Weber number may be written as : W e = ρ v 2 l σ ( displaystyle mathrm ( We ) = ( \frac ( \rho , v ^ ( 2 ) , l ) ( sigma ) ) ) where ρ ( displaystyle \rho ) is the density of the fluid ( kg / m ). v is its velocity ( m / s ). l is its characteristic length, typically the droplet diameter ( m ). σ ( displaystyle sigma ) is the surface tension ( N / m ). The modified Weber number, W e ∗ = W e 12 ( displaystyle mathrm ( We ) ^ ( * ) = ( \frac ( mathrm ( We ) ) ( 12 ) ) ) equals the ratio of the kinetic energy on impact to the surface energy, W e ∗ = E k i n E s u r f ( displaystyle mathrm ( We ) ^ ( * ) = ( \frac ( E_ ( mathrm ( kin ) ) ) ( E_ ( mathrm ( surf ) ) ) ) ), where E k i n = π ρ l 3 U 2 12 ( displaystyle E_ ( mathrm ( kin ) ) = ( \frac ( pi \rho l ^ ( 3 ) U ^ ( 2 ) ) ( 12 ) ) ) and E s u r f = π l 2 σ ( displaystyle E_ ( mathrm ( surf ) ) = pi l ^ ( 2 ) sigma ). Applications One application of the Weber number is the study of heat pipes. When the momentum flux in the vapor core of the heat pipe is high, there is a possibility that the shear stress exerted on the liquid in the wick can be large enough to entrain droplets into the vapor flow. The Weber number is the dimensionless parameter that determines the onset of this phenomenon called the entrainment limit ( Weber number greater than or equal to 1 ). In this case the Weber number is defined as the ratio of the momentum in the vapor layer divided by the surface tension force restraining the liquid, where the characteristic length is the surface pore size. References Jump up ^ Arnold Frohn ; Norbert Roth ( 27 March 2000 ). Dynamics of Droplets. Springer Science & Business Media. pp. 15 --. ISBN 978 - 3 - 540 - 65887 - 0. Jump up ^ Philip Day ; Andreas Manz ; Yonghao Zhang ( 28 July 2012 ). Microdroplet Technology : Principles and Emerging Applications in Biology and Chemistry. Springer Science & Business Media. pp. 9 --. ISBN 978 - 1 - 4614 - 3265 - 4. Further reading Weast, R. Lide, D. Astle, M. Beyer, W. ( 1989 - 1990 ). CRC Handbook of Chemistry and Physics. 70th ed. Boca Raton, Florida : CRC Press, Inc... F - 373,376. Dimensionless numbers in fluid mechanics Archimedes Atwood Bagnold Bejan Biot Bond Brenner Brinkman Capillary Cauchy Chandrasekhar Damköhler Darcy Dean Deborah Dukhin Eckert Ekman Eötvös Euler Froude Galilei Graetz Grashof Görtler Hagen Iribarren Keulegan -- Carpenter Knudsen Laplace Lewis Mach Marangoni Morton Nusselt Ohnesorge Péclet Prandtl magnetic turbulent Rayleigh Reynolds magnetic Richardson Roshko Rossby Rouse Schmidt Scruton Sherwood Shields Stanton Stokes Strouhal Stuart Suratman Taylor Ursell Weber Weissenberg Womersley Retrieved from `` https://en.wikipedia.org/w/index.php?title=Weber_number&oldid=786896735 '' Categories : Dimensionless numbers Fluid dynamics Dimensionless numbers of fluid mechanics Talk Contents About Wikipedia Bosanski Català Deutsch Español فارسی Français हिन्दी Italiano עברית Nederlands 日本 語 Polski Português Русский Slovenščina Српски / srpski Suomi Українська 中文 10 more Edit links This page was last edited on 22 June 2017, at 07 : 11. Text is available under the Creative Commons Attribution - ShareAlike License ; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia ® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization. About Wikipedia

Question: ratio of inertial force to surface tension is known as
Answer: The Weber number (We)