Giovanni Battista Venturi designed converging-diverging tubes known as Venturi tubes for experiments on fluid pressure reduction effects when fluid flows through chokes (Venturi effect). German engineer and inventor Ernst Körting supposedly switched to a converging-diverging nozzle in his steam jet pumps by 1878 after using convergent nozzles but these nozzles remained a company secret. Later, Swedish engineer Gustaf de Laval applied his own converging diverging nozzle design for use on his impulse turbine in the year 1888.