Flow diagnostics

The measurement of flow properties within fluid handling systems is of utmost importance for efficient operation and control of such systems. For single phase flow systems, extensive research has been carried out world over to diagnose the flow properties both globally and locally. Considerable advancements are being made to perfect these technologies. For multiphase flows there is still a lot of scope for technological development that needs to take place to diagnose the flow conditions accurately efficiently and effectively. In this present paper two methods are described that can be used effectively for measurement of flow properties in solid-liquid flows and gas-liquid flows. One of the methods relies on isokinetic sampling used in conjunction with impact probe for the determination of solid distribution and solid velocity in solid-liquid flows through a pipeline. The other method relies on electrical resistance method to calculate local flow velocity corresponding to the dispersed phase as well as volume fraction and interfacial area concentration

ESTIMATING INCIDENT SOLAR RADIATION IN TROPICAL ISLANDS WITH SHORT TERM WEATHER DATA

Solar radiation incident on a particular location depends on geographical and meteorological factors and as such vary spatially as well as temporally. For any given solar radiation related application an accurate prediction of incident solar radiation is important. However due to high cost of measuring and recording, solar radiation data are confined generally to a few locations, for example in Sri Lanka it is confined only to the capital city, Colombo. As such, a correlation to predict incident solar radiation based on meteorological and geographical parameters will have to be identified and validated taking into account the climatic differences in tropical regions with localized variations. In addition, due to non-availability of accurate historical meteorological data, estimated percentage variations are identified which can be used to predict incident solar radiation at a given location when two broad climatic regions are defined

Development of Novel Vehicle Design Modelling Functions for Quantifying Vehicles’ Shapes

The inland goods transportation sector has become dominant by high fuel consuming heavy goods vehicles, which are more commonly known as truck-trailer units. Manufacturers have been trying to design aerodynamically efficient truck-trailer units to reduceever increasing fuel costs. The scope for streamlining the shape of the truck-trailer unit is severely limited due to legally imposed dimensional restrictions. The development of truck-trailer prototypes is both time consuming and costly. Hence, in the present study, a novel mathematical model has been developed to generate the shape of a truck-trailer units.Furthermore, Computational Fluid Dynamics (CFD) based techniques have been employed to analyse the aerodynamic performance of the truck–trailer unit. It has been noticed that the developed vehicle modelling functions are accurate, inexpensive, user-friendly and robust. These vehicle modelling functions are expected to aid the truck-trailer manufacturers for optimising vehicle shapes

Development of novel vehicle design modelling functions for quantifying vehicles’ shapes

The inland goods transportation sector has become dominant by high fuel consuming heavy goods vehicles, which are more commonly known as truck-trailer units. Manufacturers have been trying to design aerodynamically efficient truck-trailer units to reduce ever increasing fuel costs. The scope for streamlining the shape of the truck-trailer unit is severely limited due to legally imposed dimensional restrictions. The development of truck-trailer prototypes is both time consuming and costly. Hence, in the present study, a novel mathematical model has been developed to generate the shape of a truck-trailer units. Furthermore, Computational Fluid Dynamics (CFD) based techniques have been employed to analyse the aerodynamic performance of the truck–trailer unit. It has been noticed that the developed vehicle modelling functions are accurate, inexpensive, user-friendly and robust. These vehicle modelling functions are expected to aid the truck-trailer manufacturers for optimising vehicle shapes

Development of a novel characterisation methodology for the aerodynamic coefficients of a tractor–trailer unit based on relative flow angles and vehicle dimensions.

Tractor–trailer units are integral part of the heavy commercial vehicle industry, used globally for goods transportation. Manufacturers have been trying to design aerodynamically efficient tractor–trailer units to reduce ever increasing fuel costs. In order to investigate the aerodynamic response of tractor–trailer units, the aerodynamic forces and moments have to be determined accurately, especially under crosswind conditions. In the present study, a computational fluid dynamics-based solver has been employed to simulate the flow field around a tractor–trailer with a view to quantify the effects of side wind and size variations on aerodynamic force moment system acting on tractor–trailer combination. It has been shown that the aerodynamic forces are significantly influenced by both the geometrical and flow characteristics. The drag, lift and side forces acting on a tractor–trailer unit are highest at relative flow angles of 15°, 30° and 90°, respectively. Aerodynamic forces and coefficients have been enumerated for these geometrical and flow conditions, and have been used to develop novel semi-empirical correlations for the aerodynamic coefficients for the tractor–trailer unit. These correlations have been shown to predict the aerodynamic coefficients for various vehicle dimensions under a range of flow conditions with reasonable accuracy

Multi tank model for energy efficient rain water harvesting

Rain Water Harvesting (RWH) to supplement service water is an important aspect of sustainable development. As such, much research has been carried out on optimizing the system components of RWH systems so that a maximum water saving efficiency (WSE) can be reached with a minimum storage capacity, enabling the outlay on capital minimized. However, if RWH is to proliferate it should be able to operate in par with centralized service water, supplying collected rain water to user points reliably. This is usually achieved by pumping the collected rain water to service points utilizing electricity, which in fact could negate the positive gains of RWH with regard to principles of sustainability. By introducing a multi tank model, where a smaller tank is installed for each floor at its roof level in addition to the main storage tank, a solution can be reached with superior system performance. In the model, the roof collection enters the top most tank first and then cascades through multiple tanks in multi story situations, before being collected in the main storage tank, vastly improving the overall energy efficiency of the system. The model, not only addresses the space and structural issues of the building but also ensures that the aesthetics of the building envelop is not disturbed due to smaller sizes of the upper tanks

Novel Geometric Modelling and Aerodynamic Characterisation Methodology for Truck-Trailer Vehicles

With the ever increasing consumer goods demand and increasing e-commerce sector, seeing truck-trailers dominate today’s roads and motorways is no strange sight. The large surface areas coupled with high operational speeds means these heavy goods vehicles produce high resistive forces, hence consuming significantly more fuel in comparison to an average family car. With increasing fuel costs truck-trailer designers are challenged to build more fuel efficient vehicles while still providing maximum cargo space. In order to be in motion, truck-trailer units must be able to overcome resistive forces such as aerodynamic drag, rolling and gravitational resistance, drivetrain resistance etc. With aerodynamic drag being the biggest resistive force at higher velocities, shape optimisation of truck-trailer units has proven to be the most effective and efficient method of making these vehicles more aerodynamic and hence, more fuel efficient. Boundary layer separation at sharp edges causes flow disturbance and creates negative pressure regions, which create more drag. By increasing the curvature of an edge the boundary layer separation can be minimised. By optimising the shape of a truck-trailer unit, the overall aerodynamic drag can be reduced. The following study utilises modern computational techniques such as computational fluid dynamics (CFD) to closely examine the effects of the aerodynamic performance of the truck-trailer unit. The local and global variations in the flow parameters have been studied. Various truck-trailer configurations with changing dimensional parameters such as overall length, height and width was studied along with the geometrical shape parameters using both qualitative and quantitative analytical techniques. The obtained data and the conclusions drawn from the studies were used to develop a parametric model in order to introduce a novel aerodynamic prediction tool, which is expected to aid the truck-trailer design process

Use of rainfall data to calculate incident solar radiation in Tropical countries

Determining the incident solar radiation for a given location is an important aspect of any solar related application. Though solar radiation data are available at weather stations, localized nature of solar radiation due to topographic and climatic parameters demands measured or calculated solar radiation values for a given location for accurate results. Many correlations have been developed over the past few decades yielding solar radiation values from various weather parameters such as daily sunshine duration, ambient temperature difference, relative humidity, cloud cover etc. However, most of the weather data are practically difficult and costly to record hence requiring a simplistic approach to the issue. For any geographical location the cloud cover plays a major role in controlling the incident solar radiation. In tropical countries, where the climate is highly humid, cloud cover is closely related to rainfall. Therefore, day time rainfall data can be taken as representative of overcast and clear days, paving the way to calculate the clearness index, KT using equations developed on cloud cover data

Best practices of the engineer to minimize construction claims in government projects in Sri Lanka

Claim is fundamentally a term for demand for additional compensation in relation to alteration in the contract or affirmation of right to property or money, concerning time and cost. If claims are not clearly resolved the claims may lead to disputes and have to follow dispute resolution methods which are time consuming and costly. However, claims are inevitable in construction projects. Since, the Engineer is the person who is responsible for administration and supervision of Works fairly and independently his role in a construction project is significant. Further, main source of finance in government construction projects is public funds. Hence, unique characteristics such as limitations in budget allocations, public accountability, transparency, media influence, legislation and policy changes, time impact and media influence will create specific claims which will increase the importance of the best practices of the Engineer. Therefore, this study explored the best practices that can be adopted to minimize claims in Sri Lankan government construction projects by the Engineer. Both, quantitative and qualitative research approaches were used to reach the aim in two stages. Firstly, thirty questionnaires were obtained to collect data on types of claims, causes of claims, effects of claims and best practices to be followed by the Engineer to minimize claims in government construction projects in Sri Lanka. Secondly, five experts were interviewed through a semi-structured interview to create links among top ten causes of claims and best practices to be followed by the Engineer to minimize claims in government construction projects in Sri Lanka. Moreover, usage of ICTAD/SBD/02 for minimizing claims by the Engineer and unique characteristics of Sri Lankan government projects which emphasise the importance of the best practices of Engineer in minimizing claims were discussed. The findings of the research proved that, in order to minimize claims in Sri Lankan government construction projects, the Engineer has a vital role to treat the causes of claims comprehensively and that will enable the smooth functioning of construction project activities without baffling consequences. For this reason, it was evident that there are specific best practices like taking timely management actions and proper contract administration should be followed by the Engineer to minimize claims, in order to achieve successful completion of the project within the originally anticipated estimated time, cost and quality

Development of solar powered pumping for the integration of rainwater harvested in multistory houses

Rain water Harvesting (RWH) is an ancient civil practice for more than 4000 years, drawing attention among scientists in recent decades in the light of potable water shortages and water based natural disasters such as draughts and flash floods. It is observed that the domestic service water (SW) usage patterns are uniform for a given scenario, where over 30% of drinking quality water being consumed for non potable uses such as we flushing, for which harvested rain water (RW) could be used. Roof Top Rain Water Harvesting Systems (RTRWHS) suitable for domestic situations are not being widely used due to non-optimizing of the system's highest cost component, the storage facility or the tank. Extensive research has produced a set of generic curves for Water Saving Efficiency (WSE) of a RTRWHS, enabling the selection of an optimum tank size for a given demand. Validation of this for Sri Lanka could provide a valuable design tool. This was undertaken using a prototype where the daily rainfall data was used with selected usages to create a substantial number of data points, which satisfy the generic curves. These data has indicated that the generic curves can be used in Sri Lanka with generally used roof types such as cement fibre and calicut tiles. In multi-story situations energy is needed for pumping collected rain water to end user points. A strategy should be developed to provide an alternative energy solution to mitigate the strain of extra energy consumption to the national power grid and the resultant Green House Gas (GHG) emissions for RWH to be a true component of sustainable development. Sri Lanka being a tropical country, solar power option is pursued as the most desirable alternative energy source. Since solar power also has high capital cost, minimization of energy used while relying on gravity systems also have been actively pursued. Identifying the suitability of positive displacement pumps over centrifugal pumps when connected to photo voltaic power source, a viable and cost effective solar pumping system is proposed to be used as an integrated draw-off device for a potential RWH system to be used in domestic situationsRain water Harvesting (RWH) is an ancient civil practice for more than 4000 years, drawing attention among scientists in recent decades in the light of potable water shortages and water based natural disasters such as draughts and flash floods. It is observed that the domestic service water (SW) usage patterns are uniform for a given scenario, where over 30% of drinking quality water being consumed for non potable uses such as we flushing, for which harvested rain water (RW) could be used. Roof Top Rain Water Harvesting Systems (RTRWHS) suitable for domestic situations are not being widely used due to non-optimizing of the system's highest cost component, the storage facility or the tank. Extensive research has produced a set of generic curves for Water Saving Efficiency (WSE) of a RTRWHS, enabling the selection of an optimum tank size for a given demand. Validation of this for Sri Lanka could provide a valuable design tool. This was undertaken using a prototype where the daily rainfall data was used with selected usages to create a substantial number of data points, which satisfy the generic curves. These data has indicated that the generic curves can be used in Sri Lanka with generally used roof types such as cement fibre and calicut tiles. In multi-story situations energy is needed for pumping collected rain water to end user points. A strategy should be developed to provide an alternative energy solution to mitigate the strain of extra energy consumption to the national power grid and the resultant Green House Gas (GHG) emissions for RWH to be a true component of sustainable development. Sri Lanka being a tropical country, solar power option is pursued as the most desirable alternative energy source. Since solar power also has high capital cost, minimization of energy used while relying on gravity systems also have been actively pursued. Identifying the suitability of positive displacement pumps over centrifugal pumps when connected to photo voltaic power source, a viable and cost effective solar pumping system is proposed to be used as an integrated draw-off device for a potential RWH system to be used in domestic situation