Detailed measurements of the coolant flow field have been made in the water passages of the cylinder head of an internal combustion engine. They were obtained by casting a transparent acrylic model of the cylinder head and using a mixture of hydrocarbon fluids at a predetermined temperature and concentration which ensured that the refractive index of the fluid was identical to that of the acrylic. This arrangement allowed the use of laser Doppler velocimetry to measure local velocities throughout the cooling passages. The results show that the flow was unevenly distributed with around three quarters of the total passing through the exhaust-portside passages and larger coolant velocities close to the top of the head than close to the gas face. The results of this study aimed to assist the improvement of the specific cylinder head design.

The application of phase-Doppler anemometer for scattering angles between the main rainbow and direct backscatter, was examined by calculating the spatial intensity distribution and the phase of the light scattered by a particle crossing the measuring volume. Geometrical optics was assumed and contributions to the scattered light due to reflection on the external surface of the particle and first internal reflection were considered. The response curve of the technique was calculated for different particle refractive indices, beam intersection angles, collection angles and spacings between the collection apertures. Linear response curves were obtained after integration of the intensity of the scattered light over sufficiently large rectangular collection apertures, but they became non-monotonic after a critical value of phase shift, which varied with the optical arrangement between around 220 ~ and 360 ~ did not scale with common scaling parameters used for forward scatter light, and limited the possible size range of the instrument for one optical arrangement. The particle refractive index determined the collection angle and limited sizing to particles with little uncertainty in refractive index, since a 5 % change in refractive index led to uncertainties in size of the order of 100%. An alternative sizing technique is suggested for the backscatter region.