Froude, William

(b. Darlington, Devonshire, England, 1810; d. Simonstown, Cape of Good Hope [now Union of South Africa], 4 May 1879)

ship hydrodynamics.

Froude (pronounced Frude) was the sixth son of Archdeacon Richard Hurrell Froude, rector at Dartington, and Margaret Spedding of Cumberland. He studied seven years at Oriel College, Oxford, where he was tutored in mathematics by his oldest brother, Robert Hurrell. (The latter was also a leader of the Oxford Movement, and it is noteworthy that William was the only member of the family who did not follow Newman into Roman Catholicism.) While subsequently occupied as a civil engineer, Froude came under the influence of I. K. Brunel, builder of both railways and oceangoing steamships, who stimulated his interest in naval architecture.

Froude retired from active civil engineering practice at the age of thirty-six, but he continued to give attention to various aspects of ship behavior, both recreational (he was an avid yachtsman) and technical. At Brunel’s request he undertook in 1856 a resistance and rolling study of the Great Eastern, and his analytical and experimental work on the subject, at full as well as reduced scale, extended to many ships over many years. Of even greater importance than his control of rolling by use of bilge keels was his promotion of resistance studies on scale models. His efforts to secure the support of the Admiralty for the construction of a model towing tank at first aroused the opposition of John Scott Russell and other members of the Institution of Naval Architects, and it was not till 1870 that the sum of £2,000 was granted for this purpose. The original tank, 250 feet in length, was built on Froude’s own land at Torquay only eight years before his death; he was ably assisted by his son, Robert Edmund Froude, who later built the Admiralty tank at Haslar.

William Froude’s great manual skill was of inestimable value in the construction and operation of the tank, and many of his model and prototype processes and instruments continue to be employed: the use of paraffin and waterline cutting machines for models; resistance recorders; governors; roll indicators; and propeller-engine dynamometers. Use of the scale model for resistance studies was based upon his hypothesis that the total resistance could be considered the sum of wave formation and skin friction and that each could be scaled independently. He showed that the wave effects would be similar in model and prototype if the velocity were reduced in proportion to the square root of the length. This is known as Froude’s law of similarity, even though it had been published by Ferdinand Reech, a professor in the school of naval architecture at Paris, in 1852 and purportedly introduced in his lectures as early as 1831. Froude formulated the law of skin-friction similarity after towing streamlined catamaran planks of various lengths and surface finishes through water over a wide range of speeds. The resistance of the smooth surfaces was found to vary with no more than the 1.85 power of the velocity, and only for the roughest did the power reach 2.0. His perceptive understanding of the effect of surface length was in close accord with present-day boundary-layer theory.

Froude was elected a fellow of the Royal Society of London in 1870. In 1876 he received both the honorary degree of LL.D. from the University of Glasgow and a Royal Medal of the Royal Society. His many writings are to be found in the Transactions of the Institution of Naval Architects and in reports to the British Association for the Advancement of Science. Froude’s last paper, published a year before his death, was on the subject of screw propulsion, one of his early interests. While on a holiday trip to the Cape in 1879 he succumbed to dysentery just before his scheduled return to England.

BIBLIOGRAPHY

I. Original Works. Froude’s writings include “Experiments on the Surface-friction Experienced by a Plane Moving Through Water,” in British Association for the Advancement of Science Report, 42nd Meeting, 1872; and “On Experiments with H.M.S. Greyhound,” in Transactions of the Institution of Naval Architects, 16 (1874), 36–73.

II. Secondary Literature. On Froude and his work, see “Memoir of the Late William Froude, LL.D., F.R.S.,” in Transactions of the Institution of Naval Architects, 20 (1879), 264–269; W. Abell, “William Froude,” in Transactions of the Institution of Naval Architects, 76 (1934), which quote his 1868 request to the Admiralty; and H. Rouse and S. Ince, History of Hydraulics (New York, 1963), pp. 243–256.

Hunter Rouse

William Froude frōōd , 1810–79, English engineer and naval architect, brother of J. Anthony Froude ; educated at Oxford. In 1837 he worked on the Bristol and Exeter railroad, constructing the line from the Whitehall tunnel to Exeter. He studied the motion of a ship among waves, demonstrating that the rolling of a ship could be reduced by a deep bilge keel. This fact and his conclusions on the relationship between construction design, efficiency, and power in screwships were extensively used by the Royal Navy. He also constructed a dynamometer for measuring the power of large marine engines.

Froude number(Fr) A dimensionless number equal to the ratio of water velocity to the speed of a gravity wave, used to assess whether flow in an open channel is critical, tranquil, or shooting. If the Froude number is less than 1, flow is said to be subcritical or slow; if Fr = 1 flow is critical; and if Fr is greater than 1 flow is fast or supercritical. It was calculated by the English engineer William Froude (1810–79).