Particle image velocimetry studies of bubble growth and detachment by high speed photography

An understanding of bubble flows is important in the design of process equipment, particularly in the chemical and power industries. In vapour-liquid processes the mass and heat transfer between the phases is dominated by the liquid-vapour interface and is determined by the number, size and shape of the bubbles. For bubble flows these characteristics are often controlled by the generation mechanisms and, since bubble flows are often generated at an orifice, it is important to determine the controlling parameters which dictate how bubbles grow and detach. For bubbles growing at orifices the liquid displacement is an important feature and affects the pressure distribution acting on the bubble and the heat and mass transfer that may occur at the bubble interface. Therefore, in this study, the characteristics of the liquid velocity field are studied experimentally using Particle Image Velocimetry (PIV) during growth, detachment and translation of a bubble being generated at an orifice supplied with a constant mass flow rate of air. The process is transient and occurs over a period of approximately 50 msecs. In order to map the transient flow field a combination of high speed cine and cross correlation PIV image processing has been used to determine the liquid velocity vector field during the bubble growth process. The paper contains details of the PIV technique and presents several of the velocity vector maps calculated

Measurement and simulation of the flow field around a triangular lattice meteorological mast

The international standard IEC 61400-12-1 “Wind turbines – Part 12-1: Power performance measurements of electricity producing wind turbines” aims to provide a uniform methodology that will ensure consistency, accuracy and reproducibility in the measurement and analysis of power performance by wind turbines [1]. Annex G of this standard provides a methodology for the appropriate arrangement of instruments on the meteorological mast to ensure accurate measurement. For cup anemometers it provides recommendations about their location relative to the mast so that the effect of mast and boom interference on their output may be minimised. These recommendations are given for both tubular masts and lattice masts. This paper compares the flow distortion predicted by the IEC standard and the results of a 3D Computational Fluid Dynamics (CFD) simulation of a triangular lattice mast. Based on the results of wind tunnel and CFD simulation it was found that the flow distortion surrounding the lattice mast was over predicted by the method suggested in appendix G of IEC61400-12-1. Using the CFD data it was possible to determine, for a range of flow directions and mast heights, the distance from the mast that anemometers would need to be in order to be outside the flow distortion field

EU-Norsewind : Investigation of flow distortion effects on offshore instrumentation

In 2008 the EC programme NORSEWInD kicked off with a mission to deliver high quality offshore wind speed data for the wind industry. The aim of the project is to deliver offshore wind speed data to the wind industry by measuring offshore wind speed data from remote sensing instruments (LiDAR) on off shore platforms. This work reports on the techniques used to assesses the interference effects of the various mounting platforms on the measured wind speed data

Accounting and estate management in North-East England c.1700-1770 with particular reference to the Bowes estates

Through the accounts, the thesis examines estate accounting and management practice in the north-east of England, with special reference to the Bowes, in order to ascertain whether estates were managed efficiently as productive investments, and whether accounting aided managerial activity at this early stage of industrial development. George Bowes was the estate proprietor for most of the period in question. His active involvement in the day-to day operations of his estates, coupled with the geographical spread of his activities and his distance from events, necessitated a centralised organisational structure, that was capable of delegating responsibility to stewards in key areas, whilst, at the same time, retaining control at the centre. This was achieved through a unified reporting network, which ensured that management and accounting practices were highly integrated over different activities. Generally, the accounts were based on the bilateral recording of cash receipts and payments, with adjustments for opening and closing debtors, creditors and stocks as appropriate. Charge and discharge accounts did not predominate. Most of the accounts were prepared by the stewards. The majority of the estate accounts were designed to keep track of rights and obligations. There was a close linkage between the form of the accounts and the mode of organisational control, and the accounting procedures were flexible enough to respond to organisational changes. Written agreements underpinned the contractual obligations of third parties, and accounts were used to monitor compliance. Internal audit checks increased their effectiveness as a control mechanism. The survival of cost analysis, profit statements and planning data indicates that profit maximisation was also an important issue - the estates were not treated simply as units of consumption - and that the accounts played an important facilitating role. Colliery viewers were instrumental here. There are indications that a knowledge-power mechanism also existed within the estates, casting doubt on both the mutual- exclusivity of particular explanations of accounting activities, and on the notion that a relevant distinction exists between 'modern' and 'pre-modern' business organisation

Measurement and simulation of the flow field around a triangular lattice meteorological mast

The international standard IEC 61400-12-1 “Wind turbines – Part 12-1: Power performance measurements of electricity producing wind turbines” aims to provide a uniform methodology that will ensure consistency, accuracy and reproducibility in the measurement and analysis of power performance by wind turbines. Annex G of this standard provides a methodology for the appropriate arrangement of instruments on the meteorological mast to ensure accurate measurement. For cup anemometers it provides recommendations about their location relative to the mast so that the effect of mast and boom interference on their output may be minimised. These recommendations are given for both tubular masts and lattice masts.This paper compares the flow distortion predicted by the IEC standard and the results of a 3D Computational Fluid Dynamics (CFD) simulation of a triangular lattice mast. Based on the results of wind tunnel and CFD simulation it was found that the flow distortion surrounding the lattice mast was over predicted by the method suggested in appendix G of IEC61400-12-1. Using the CFD data it was possible to determine, for a range of flow directions and mast heights, the distance from the mast that anemometers would need to be in order to be outside the flow distortion field

Feasibility study for estimating the offshore shear layer from on shore measurements

This paper presents an open source computational fluid dynamics (CFD) study of air flow over a complex terrain. The open source C++ toolbox OpenFOAM has been used for the CFD analysis and the terrain considered is a scale model of Berlengas Island, which lies close to the Portuguese coast. In order to validate the CFD model, experimental work has been carried out in an open-section wind tunnel using hot-wire anemometry to measure the wind profiles above the island. In the majority of cases, the OpenFOAM CFD solutions show very good agreement with the experimental wind profile data, confirming that open source CFD solutions are possible for environmental flows over complex terrain. Such an analysis demonstrates the feasibility of estimating offshore boundary layer effects from onshore measurements

A CFD technique for estimating the flow distortion effects on LiDAR measurements when made in complex flow fields

The effect of flow distortion on the measurements produced by a LiDAR or SoDAR in close proximity to either complex terrain or a structure creating localised flow distortion is difficult to determine by analytical means. Also, as LiDARs and SoDARs are not point measurement devices, the techniques they employ for velocity measurements leads to complexities in the estimation of the effect of flow distortion on the accuracy of the measurements they make. This paper presents a method by which the effect of flow distortion on measurements made by a LiDAR in a distorted flow field may be determined using computational fluid dynamics. The results show that the error created by the flow distortion will cause the vector measured by a LiDAR to differ significantly from an equivalent point measurement. However, the results of the simulation show that, if the LiDAR is being used to measure the undisturbed flow field above a structure which creates highly localised flow distortion, the LiDAR results are less affected by the distortion of the local flow field than data acquired by a point measurement technique such as a cup anemometer

Two-beam lidar measurements in a non-homogeneous wind field

Nacelle based wind lidars are designed to sit atop a wind turbine structure and make measurements at given distances from it. Most times the lidar faces the turbine’s upstream direction to sense oncoming wind. Two lidars were set up looking upstream on two adjacent offshore turbines in Denmark. The case considered was for when the turbines were oriented such that one lidar was looking into the free stream while the other lidar had one beam in the first turbine’s wake and the other beam in near free stream conditions. This enabled the possibility to look at horizontal wind speeds reconstructed inside homogeneous and non-homogeneous wind fields. Data for the two lidars were processed and averaged over different intervals. Correlations of radial and horizontal wind speeds in different wind fields were performed. Results in this case show horizontal wind speeds reconstructed in non-homogeneous field similar to those reconstructed in a (assumed) homogeneous one

The Limits of Unlimited War: American Victory Doctrine From Unconditional Surrender to Peace With Honor, 1943-1973

My dissertation explains the remarkable reversal in U.S. foreign policy from victory at all costs in World War II to peace at any price in the Vietnam War. Between 1943 and 1973, the United States enacted an astonishing strategic and moral volte-face; from unconditional surrender to peace with honor, from unlimited war to limited war, and from an unwavering will to win against Germany and Japan to a desperate desire to escape Vietnam. Certainly, the shift from unconditional surrender and total victory in World War II to peace without conquest and peace with honor in Vietnam represented a change in American goals, while the turn from total or unlimited war to limited war signified a change in American strategies. But these changes were not merely evident alterations or evolutions of U.S. grand strategy and foreign policy, they indicated a less visible metamorphosis in American morality. Indeed, I argue that the decline of victory doctrine led the United States from victory at all costs to peace at any price. In World War II, victory had been the supreme moral and strategic consideration but, after Japan&rsquo;s unconditional surrender, U.S. strategists, commentators, and public opinion came to believe that total victory was immoral and impossible. As victory became less ethical &ndash; a shift called &ldquo;debellicization&rdquo; &ndash; and as minimizing casualties became more virtuous &ndash; a change I call &ldquo;moral inflation&rdquo; &ndash; Americans determined that victory was no longer worth the cost. The nuclear revolution thwarted America&rsquo;s annihilation strategy and made it impossible for the United States to win a war at acceptable cost while the nuclear taboo prevented presidents and their advisors from employing nuclear weapons. Limited wars also became unwinnable. Stalemate in Korea led U.S. strategists to negotiate an armistice, while the futility of guerrilla fighting in Indochina made them anxious to escape the Vietnam quagmire. Finally, U.S. strategists turned against killing and dying as their valuations of both American and enemy lives increased. Together, debellicization and moral inflation caused the United States to lose the disposition, determination, and willingness to pay the price of victory.</p