Bagnold number [SEP] named after
Bagnold number
The Bagnold number (Ba) is the ratio of grain collision stresses to viscous fluid stresses in a granular flow with interstitial Newtonian fluid, first identified by Ralph Alger Bagnold. 
The Bagnold number is defined by 
where formula_2 is the particle density, formula_3 is the grain diameter, formula_4 is the shear rate and formula_5 is the dynamic viscosity of the interstitial fluid. The parameter formula_6 is known as the linear concentration, and is given by
where formula_8 is the solids fraction and formula_9 is the maximum possible
Bagnold Dunes" on Mars' surface being named after him by the organization.
During World War 2 he was a soldier in the British Army, in which he founded the behind-the-lines reconnaissance, espionage and raiding unit the "Long Range Desert Group", serving as its first commanding officer in the North Africa Campaign.
Early life.
Bagnold was born in Devonport, England. His father, Colonel Arthur Henry Bagnold (1854–1943) (Royal Engineers), participated in the rescue expedition of 1884–85