In this thesis a new type of Mass Flow Controller (MFC) is designed, constructed and used. Whilst existing MFCs rely on either pressure loss or temperature rise measurements to estimate and control flows, this new device is based on measuring time, which is more easily and accurately monitored. The device adopts the 'bucket and stopwatch' method to deliver specific and constant masses at pre-set time intervals. By alerting the time intervals, the mass flow is precisely controlled.

In recent years there has been a great deal of interest in understanding the fundamental behaviour of granular materials. Granular materials are ubiquitous in natural and industrial settings however, their flow behaviour cannot be described using classical ideas of fluid flows as they stand. Of particular interest are theories which have been developed over the last 25 years.

Incompressible Taylor-Couette flow has been studied extensively over the years. However, the compressible system has been largely ignored with only a few notable studies. The present thesis aims to explore the compressible Taylor-Couette system for a large range of parameters. The compressible equations have been linearised and a spectral method was applied to solve the system using a MATLAB-routine. In Chapter 2, we discuss the analysis performed to solve the system and explain the basic concepts and phenomena we expect to find. We also explain the numerical methods used. Chapter 3 discusses the case in which the outer cylinder remains motionless. The most important parameters, the Mach and Prandtl number and the radius ratio, are varied. In Chapters 4 and 5, the same procedure is applied to the cases of the co- and counter-rotating cylinders, respectively.

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In this work I shall give details of the development of a two dimensional Lattice Boltzmann algorithm targeting the simulation of immiscible fluids at low Reynolds number and low Capillary number. The Lattice Boltzmann method will be explained along with its multi-component extensions. Key method developments shall first be developed in terms of single component advancements, made in the lattice closure algorithm and in the application of external forces to boundary lattice sites. Having secured single component advancements, I shall present parallel developments made in immiscible flow simulation, considering two immiscible fluids (however extension to larger numbers of immiscible species is mentioned where appropriate). Drop dynamics within shear flow shall be examined with Numerical colour segregation along with attempts for the application of a kinematic condition. Analytic segregation shall then be used and the dynamics of the phase field shall be analysed showing improved drop dynamics. A simple and adaptable method for application of a kinematic condition shall next be shown to be effective when used in conjunction with the analytic diffusion method in improving the quality of the models hydrodynamics. Culmination of all the previously identified improvements to the simulation method shall then be utilised in the simulation of wetting drops in both static and dynamic situations. The final method is qualitatively shown to predict static wetting, rolling contact points, bifurcating contacts and the spreading of films.

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Most flows of practical importance are governed by viscous near-wall phenomena leading to separation and subsequent transition to a turbulent state. This type of problem currently poses one of the greatest challenges for computational methods because its characteristics covers a wide range of physical processes that often place contradictory requirements on the numerics employed. This thesis seeks to investigate the physics of complex, separated flows pertinent to aeronautical engineering and to assess the performance of variants of the Implicit Large-Eddy Simulation approach in predicting this type of problem realistically. For this purpose, different numerical solution strategies based on high-resolution methods, distinguished by their order of accuracy, are used in precursor simulations and one selected approach is applied to a fully three-dimensional wing flow. In order to isolate the development from laminar to turbulent flow after separation has occurred, the prototype Taylor-Green Vortex is considered. Here, the behaviour of the numerical schemes during the linear, non-linear and fully turbulent stages in the flow evolution is tested for different grid sizes. It is found that the resolution power and the likelihood of symmetry breaking is increasing with the order of accuracy of the numerical method. These two properties allow the flow to develop more realistically on coarse grids if higher order schemes are employed. In the next step, flow separation from a gently curved surface is included. The fundamental study of a statistically two-dimensional channel flow with hill-type constrictions demonstrates the basic applicability of ILES to problems featuring massive separation. Without specific wall-treatment, high-resolution methods can improve prediction of the detachment location when compared to classical Large-Eddy Simulations. Finally, an ILES simulation of three-dimensional flow over a swept wing geometry at moderate angle of incidence is presented. The results are in excellent agreement with experiment in the fully separated and turbulent region and they are more accurate than a classical hybrid RANS/LES approach, using a grid twice the size, over the majority of the wing. This outcome will probably settle the dispute that has erupted in the past over the applicability of ILES to complex, wall-bounded flows.

To date the influence of bed roughness onl the propagation and dynamics of gravity currents has been largely neglected. A new physical modelling dataset has been compiled, which details the fundamental affects of several bed roughnesses on lock-release gravity currents. Five bed configurations were chosen encompassing 'grain' and 'form' type elements at a range of spacings. 1%, 5% and 10% initial density excesses were studied and the effect of removing the buoyant ambient fluid between the elements examined. Observations due to changing the current depth relative to the element height were also made. Ultrasonic Doppler velocimetry profiling (UDVP) and video capture techniques were used to analyse stream wise and vertical velocity structures and the affects on the front speed and distance travelled by the current. A 10 depth-averaged model solves modified 2-layer shallow water equations using the method of characteristics to obtain temporal velocity and depth evolution for a current under the influence of a general roughness quantity. 2D and 3D depth-resolved CFD simulations use the commercial software FLUENT to solve the RANS equations and transport of a scalar for the dense current with the RNG k - € turbulence model. The CFD predictions were well validated by the new experimental dataset and provide supplementary predictions of concentration, lateral motion and activity in the vicinity of the roughness elements. Comparison of 20 and 30 models resulted in the conclusion that the 3D model is vital for accurate simulation of internal dynamics of gravity current propagation over beam type bed roughness. In general general, the distance that the front travels decreases with any bed roughness present. This reduction increases with element spacing. The stream wise mean velocity profiles show a reduced velocity maximum further from the bed. Decreased entrainment results from breakdown of larger billows. Also observed is a thicker current, a rounder profile and a shorter, diluted head. Areas of increased vertical motion within the current. associated with decreased horizontal motion are observed, indicative of ejections of ambient fluid from between the elements. The presence of this fluid is found to contribute to ~ 50% of the current retardation. There are also similarities with the effects of bed roughness in open channel and pipe flows, most notably there is a critical element spacing (11'/ kr ~ 7) where the effects of roughness are greatest (where w is element spacing and kr is element height). The experimental and numerical results demonstrate that the application of existing models that rely on experimental validation with smooth beds to situations where a rough boundary is present may lead to significant errors.