Fully developed air flow has been investigated over a Reynolds-number range of 82800-346700 in a duct that simulates two interconnected subchannels of a rod bundle with a pitchldiameter ratio of 1.20. Based on equivalent hydraulic diameter, friction factors were found to be 2% lower than for pipe flow. Detailed measurements were made at a Reynolds number of 200000 of axial velocities, secondary velocities, and the Reynolds stresses. The distribution of axial velocity near the walls (normalized with the local friction velocity) could be expressed by an inner law of the wall for y+ up to 1500. Distributions of the normal Reynolds stresses and the mean turbulence kinetic energy were similar to those observed in a number of pipe and two-dimensional channel flows and could be correlated using the axial-velocity fluct,uations normalized with the local friction velocity. Maximum secondary velocities were about 1.5 % of the bulk axial velocity. The ‘k-ε’ turbulence model and an algebraic vorticity source for generating secondary velocities enabled the computation of axial velocities, secondary velocities, and mean turbulence kinetic energies that are in satisfactory agreement with those measured.

Spatial growth of mechanically generated water waves under the action of wind has been measured in a laboratory wind-wave flume both for pure water and for water containing a surfactant (sodium lauryl sulphate, concentration 2.6 × 10−2%). I n the latter case, no wind waves develop on the surface of the mechanically generated waves as well as on the still water surface for wind speeds up to U10≈ 15 m/s, where U10 is the wind velocity at the height Z = 10 m. Therefore we can study the wind-induced growth of monochromatic waves without the effects of co-existing short wind waves. The mechanically generated waves grew exponentially under the action of the wind, with fetch in both cases. The measured growth rate β for the pure water can be fitted by β/f = 0.34(U*/C)2 0.1 [lsime ] U*/C [lsime ] 1.0, where f is the frequency of the waves, C is the corresponding phase velocity, and U, is the friction velocity obtained from vertical wind profiles. The effect of the wave steepness H/L on the dimensionless growth rate β/f is not clear, but seems to be small. For water containing the surfactant, the measured growth rate is smaller than that for pure water, but the friction velocity of the wind is also small, and the above relation between β/f and U*/C holds approximately if the measured friction velocity U* is used for the relation.

Inviscid transonic shear flow in a rectangular channel is considered; opposite walls are parallel except in the region of interest, where one pair of opposing walls form a nozzle-like constriction. The flow exhibits the essential features found in an axial-flow rotor of zero stagger angle, where the relative velocity is transonic, the constricted passage being similar to the channel formed between two adjacent blades. Analytical solutions, valid to second order, are presented for the case where the ratio of the order of the change in velocity caused by the variation in flow area to the order of the change in velocity across the channel due to the shear is unity. The case where this ratio is small compared with one is discussed, as is the problem formulation for a flow with a shock wave in the passage

Solutions for interfacial waves of permanent form in the presence of a current wcre obtained for small-to-moderate wave amplitudes. A weakly nonlinear approximation was used to give simplc analytical solutions to second order in wave height. Numerical methods were usctl to obtain solutions for larger wave amplitudes, details are reported for a number of sclccted cases. A special class of finite-amplitude solutions, closely related to the well-known Stokes surface waves, were identified. Factors limiting the existencc of steady solutions are examined.

The motion of free surfaces in incompressible, irrotational, inviscid layered flows is studied by evolution equations for the position of the free surfaces and appropriate dipole (vortex) and source strengths. The resulting Fredholm integral equations of the second kind may be solved efficiently in both storage and work by iteration in both two and three dimensions. Applications to breaking water waves over finite-bottom topography and interacting triads of surface and interfacial waves are given.

Fully developed laminar flow for a horizontal heated curved tube is studied numerically. The tube is heated so as to maintain a constant axial temperature gradient. A physical model is introduced that accounts for the combined effects of both buoyancy and centrifugal force. Results, for a Prandtl number of one, are presented for a moderate range of Dean numbers and the product of the Reynolds and Rayleigh numbers. Detailed predictions of the flow resistance, the average heat-transfer rate and the secondary-flow streamlines are given. Also presented are results on the position of the local maxima of shear stress and heat-transfer rate. The numerical results reveal that the mass-flow rate is drastically reduced owing to the secondary flow for a given axial pressure gradient. Consequently, the total heat- transfer rate decreases for a more-curved tube as well as for a larger axial temperature gradient. A flow-regime map is provided to indicate the three basic regimes where (i) centrifugal force dominates, (ii) both buoyancy and centrifugal forces are important, and (iii) buoyancy force dominates.

The mean-velocity profiles and entrainment rates in the similarity region of a two-dimensional jet are generated by a simple superposition of Rankine vortices arranged to represent a vortex street. The spacings between the vortex centres, their two-dimensional offsets from the centreline, as well as the core radii and circulation strengths, are all governed by similarity relationships and based upon experimental data.

Major details of the mean flow field such as the axial and lateral mean-velocity components and the magnitude of the Reynolds stress are properly determined by the model. The sign of the Reynolds stress is, however, not properly predicted.