 product uniform shear flow wind tunnel product uniform shear flow wind tunnel uniform shear flow work wind tunnel insert grid parallel rod vari space function grid impos resist flow grade work produc linear variat total pressur larg distanc downstream introduc appreci gradient static pressur grid method calcul suitabl arrang rod describ method strictli applic weakli shear flow experi grid design shear paramet larg 0 45 close agreement theori evid experi larg-scale secondari flow accompani shear--a danger inher empir attempt grade resist grid--nor tendenc observ shear decai increas distanc grid 