The early stages of propagation of a water hammer disturbance are investigated, water hammer constituting a special case of axially symmetric elastic wave propagation in a fluid-filled cylindrical shell. Many of the objectionable features of the elementary (Joukowsky) water hammer theory are removed, and particular emphasis is placed upon consideration of the effects of radial inertia of the fluid and of the shell. The formulation is appropriate for consideration of any axially symmetric acoustic disturbance which originates in the fluid and any of the usual engineering boundary conditions which describe constraints on motion of the end, or ends, of the shell. Motion of the shell is described by a thin-shell theory, and motion of the fluid is described by the axially symmetric wave equation, nonhomogeneous boundary conditions providing coupling of the fluid and shell motions. Application of a finite Hankel transform to the axially symmetric wave equation yields an infinite system of one-dimensional wave equations representing motion of the fluid. Integration of a finite set of these wave equations in conjunction with equations governing motion of the shell is accomplished numerically after a straight-forward application of the method of characteristics. An analysis which includes bending, rotary inertia, and shear deformation in the shell is conducted for the case of sudden termination of uniform flow in a semi-infinite shell with a"built-in" end. For a relatively thick steel shell filled with water it is found that bending stresses and transverse shearing stresses at the end of the shell are significant, but that nowhere are there significant longitudinal membrane stresses. Maximum stresses and displacements are found to occur within the time required for an acoustic disturbance in unbounded fluid to traverse one diameter of the shell. The maximum radial displacement of the middle surface of the shell is found to exceed the value predicted by the elementary theory by about fifty percent. A solution based on the classical membrane theory of shells, neglecting longitudinal stresses, also is obtained by numerical integration of the ordinary differential equations arising from application of the method of characteristics to the governing partial differential equations. Considerable simplification of the numerical calculations results from the fact that only one pair of families of characteristic lines are involved in the membrane analysis as compared to three pairs of such families in the bending analysis. The membrane analysis is employed principally to show the adequacy of using the first five of the infinite set of one-dimensional wave equations governing motion of the fluid. The membrane formulation takes account of two important omissions of the elementary theory, namely radial inertia of the fluid and radial inertia of the shell. A representation of the fluid motion by a single one-dimensional wave equation is investigated. Radial inertia of the fluid is taken into account by attributing additional mass to the shell. This formulation is shown to produce the same results as the best available long-time asymptotic solution to a water hammer problem, but it is found, on the basis of an analysis employing the membrane theory of shells, to be inadequate for describing the early stages of a water hammer disturbance. / Doctor of Philosophy

Real-time digital music system design often involves the translation of formal music notation or human gestures by some input device to Musical Instrument Digital Interface (MIDI) commands which are then transmitted to an electronic music synthesizer. This thesis describes the design and implementation of a microprocessor controlled input device that maps analog signals to MIDI commands and transmits them to a digital synthesizer in real time. The controller emulates a traditional acoustic folk instrument known as a hammer dulcimer. The hammer dulcimer is the forerunner of the keyboard family of instruments and incorporates features found in percussive and keyboard instruments. As with any acoustic instrument, its tone is a composite of several partial tones. The controller, in emulation mode, generates the fundamental tone and optionally outputs the partials tones with the just noticeable difference (JND) tolerances described in psychoacoustic research. This feature allows the designer to experiment with the timbre of the fundamental tome. The controller interface succeeds in capturing the gestural movements and translating these events to MIDI commands. It also provides features such as on-demand retuning which allows the musician to play in any tonal center without changing hand positions. Selected MIDI features such as the pitch bend, program change and sustain are implemented by the controller. The prototype instrument yields a tow octave range from an eight by eight inch sensor grid. Additional grids can be added to increase the range of the instrument. / Master of Science

This master thesis project was done in collaboration with Epiroc Group Ab. Epiroc supplies high-quality drills of various types that can be used both above and below ground. A major problem in their percussive rock drills is that that cavitation is formed. Cavitation is a phenomenon that occurs when a fluid is subject to a sudden pressure drop. This pressure drop causes the liquid to vaporize and create gas bubbles. These gas bubbles will cause erosion to the walls when imploded. These cavitation damages lead to drills breaking and parts having to be replaced preserved. An experimental rig was used to create cavitation. From the experimental rig, it was possible to measure the hydraulic transients that are created when the valve was closed. In this study, we examined whether one can visually see these damages occurring inside the pipe on valve parts that are subjected to these cavitation damages. CFD simulations were used to re-create the closing of the valve in the experimental rig. By exporting pressure data from the experiments one could compare the numerical result to the experimental data. It was also investigated if it is possible to see some connection between the gas formation and the damages seen visually from the experimental part. For the simulation the realizable k − ε methods were implemented with enhanced wall treatment. The mixture model was used since we have a multi-phase flow. Some visual damages were recognized during the experiments. However, no distinguished pattern or specific areas was established. From the simulations, it could be determined that they generated gas when the valve was closed. However, the pressure transients could not be replicated in the numerical result.

No description available.

yes / This paper models a hydro turbine based on the dynamic description of the hydraulic system having a surge tank and elastic water hammer. The dynamic of the hydraulic system is transformed from transfer function form into the differential equation model in relative value. This model is then combined with the motion equation of the main servomotor to form the nonlinear model of the hydro turbine, in which the power of the hydro turbine is calculated using algebraic equation. A new control model is thus proposed in which the dynamic of the surge tank is taken as an additional input of control items. As such, the complex hydraulic system is decomposed into a classical one penstock and one machine model with an additional input control. Therefore, the order of the system is descended. As a result, the feasibility of the system is largely improved. The simulated results show that the additional input of the surge tank is effective and the proposed method is realizable. / National Natural Science Foundation of China (50839003, 50949037, 51179079), Natural Science Foundation of Yunnan Province (No. 2008GA027)

Carregamentos transientes termo hidráulicos do tipo Steam Hammer são eventos comuns em sistemas de tubulações de vapor com grandes potenciais de catástrofes em plantas de geração de energia. Uma vez iniciado o evento, ondas de pressões são geradas com amplitudes, geralmente, de grande magnitude ocasionando altas pressões no sistema, ruídos, deformações, fadiga, com possibilidade de danos materiais e econômicos e em casos extremos fatalidades. Os procedimentos da indústria para análise deste tipo de sistema consistem realização de análises estáticas equivalentes ou análise de espectro de resposta com carregamentos caracterizados por meio de métodos analíticos baseados em hipóteses simplificadoras do fluido e fluxo. Neste trabalho é proposta a analise de sistema de tubulações por meio do método de integração numérica com superposição modal e carregamento caracterizado por método numérico com base no método das características. Comparações foram efetuadas entre os resultados obtidos pela metodologia proposta e os procedimentos da indústria, demonstrando que, dado ao alto grau de conservadorismo, os procedimentos da indústria acarretam em superdimensionamento de estruturas e tubulações ocasionando custos adicionais de projeto, sendo a otimização do projeto obtida aplicando-se a metodologia proposta no trabalho. / Steam Hammer is a common transient thermo hydraulic event in steam piping systems with potential to cause serious damages in power generation plants. It generates pressure waves, generally of great amplitude and magnitude, causing high pressures in the system, associated with noise, with possible material and economic damages and, in extreme case, even fatalities. Industry procedures for analysis of these events consists of performing equivalent static analysis, or response spectrum analysis, with transient loadings calculated by analytical methods based on assumptions of fluid and flow. This paper proposes a new methodology for the piping system analysis by the numerical integration method with modal superposition and transient loadings calculated by a numerical method based on the method of characteristics. Comparisons were made between the results obtained by the proposed methodology and the stablished industry procedures, confirming that, due to the high degree of conservatism, industry procedures can lead to additional cost to the design, with the optimization of the design being obtained by applying the methodology proposed in this paper.

Carregamentos transientes termo hidráulicos do tipo Steam Hammer são eventos comuns em sistemas de tubulações de vapor com grandes potenciais de catástrofes em plantas de geração de energia. Uma vez iniciado o evento, ondas de pressões são geradas com amplitudes, geralmente, de grande magnitude ocasionando altas pressões no sistema, ruídos, deformações, fadiga, com possibilidade de danos materiais e econômicos e em casos extremos fatalidades. Os procedimentos da indústria para análise deste tipo de sistema consistem realização de análises estáticas equivalentes ou análise de espectro de resposta com carregamentos caracterizados por meio de métodos analíticos baseados em hipóteses simplificadoras do fluido e fluxo. Neste trabalho é proposta a analise de sistema de tubulações por meio do método de integração numérica com superposição modal e carregamento caracterizado por método numérico com base no método das características. Comparações foram efetuadas entre os resultados obtidos pela metodologia proposta e os procedimentos da indústria, demonstrando que, dado ao alto grau de conservadorismo, os procedimentos da indústria acarretam em superdimensionamento de estruturas e tubulações ocasionando custos adicionais de projeto, sendo a otimização do projeto obtida aplicando-se a metodologia proposta no trabalho. / Steam Hammer is a common transient thermo hydraulic event in steam piping systems with potential to cause serious damages in power generation plants. It generates pressure waves, generally of great amplitude and magnitude, causing high pressures in the system, associated with noise, with possible material and economic damages and, in extreme case, even fatalities. Industry procedures for analysis of these events consists of performing equivalent static analysis, or response spectrum analysis, with transient loadings calculated by analytical methods based on assumptions of fluid and flow. This paper proposes a new methodology for the piping system analysis by the numerical integration method with modal superposition and transient loadings calculated by a numerical method based on the method of characteristics. Comparisons were made between the results obtained by the proposed methodology and the stablished industry procedures, confirming that, due to the high degree of conservatism, industry procedures can lead to additional cost to the design, with the optimization of the design being obtained by applying the methodology proposed in this paper.

Thesis (MScEng (Civil Engineering))--Stellenbosch University, 2008. / There are currently well established compaction methods being used in laboratories globally to prepare specimens for material testing. None of these methods provides the repeatability and reproducibility, ease of execution or simulation and correlation to field compaction desired by engineers. The research presented in this report was aimed at the development of a new or adapted compaction method for bituminous stabilized materials (BSM) that would address the aforementioned factors, by making use of a vibratory hammer. Along with this, a new protocol was to be established. The initial vibratory hammer that was tested was the Kango 637®. This specific vibratory hammer suffered irreparable damage to the gearbox during the research. A replacement Kango hammer could not be purchased, therefore a substitute hammer was purchased i.e. a Bosch GSH 11E®, for which back-up service and replacement parts are readily available throughout South Africa. Significant progress had been made with the development of a laboratory compaction protocol for BSM using the Kango Hammer. The specifications of the Bosch® hammer showed it was superior in terms of power, weight and other technical features. Comparative testing was therefore carried out. This allowed for the adaptation of the results achieved to that point. Extensive experimentation was then carried out using two types of BSM i.e. foamed bitumen (80/100 bitumen) and bitumen emulsion (60/40 Anionic Stable Grade) stabilized material. The initial material used for the experimentation was a G2 quality graded crushed stone. Additional material was also obtained from a recycling project taking place along the N7 near Cape Town. The N7 material was used to perform correlation experiments so as to determine how representative the laboratory compacted specimens were to field compacted material. Results showed that the vibratory hammer is capable of producing specimens for testing in the laboratory as well as providing a possible benchmark method for accurately controlling the quality of work on site i.e. field density control. This was done by identifying the time to and level of refusal density compaction. The level of refusal density compaction was expressed as a percentage of Mod AASHTO compaction and using current specifications, a potentially new site compaction level specification was determined. In order to asses the material applicability of the vibratory hammer compaction method, tests regarding moisture sensitivity analysis were carried out on a G5 material. The vibratory compaction protocol includes a specification for the type of hammer, guide-frame, surcharge weight, compaction moisture and number of layers. Vibratory compaction can be used to prepare two types of specimens: • Specimens for triaxial testing with a diameter of 150mm and a height of 300mm • Specimens for laboratory testing with a diameter of 150mm and a height of 125mm. Tests showed that the material properties prove to have an influence on the compactability of the material. Material from the N7 recycling project had been milled out thus altering the grading and including some RAP. This in turn influenced compaction. The vibratory hammer moisture curve was found to shift slightly to the left when compared to the Mod AASHTO moisture curve. The variability of the vibratory hammer was found to be well below the specified variability of 15%. Repeatability experiments on G5 material indicate that vibratory hammer compaction may be used on lesser quality granular materials. A recommended procedure for the compaction of BSM was developed following the experimentation results.

Thesis (MScEng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Presented here is an Eulerian scheme for solving the unsteady pipe-flow equations. It is called the Characteristic Dissipative Petrov-Galerkin finite element algorithm. It is based on Hicks and Steffler's open-channel finite element algorithm [5]. The algorithm features a highly selective dissipative interface, which damps out spurious oscillations in the pressure field while leaving the rest of the field almost unaffected. The dissipative interface is obtained through upwinding of the test shape functions, which is controlled by the characteristic directions of the flow field at a node. The algorithm can be applied to variable grids, since the dissipative interface is locally controlled. The algorithm was applied to waterhammer problems, which included reservoir, deadend, valve and pump boundary conditions. Satisfactory results were obtained using a simple one-dimensional element with linear shape functions. / AFRIKAANSE OPSOMMING: 'n Euleriese skema word hier beskryf om die onbestendige pypvloei differensiaal vergelykings op te los. Dit word die Karakteristieke Dissiperende Petrov-Galerkin eindige element algoritme genoem. Die algoritme is gebaseer op Hicks en Steffler se oop-kanaal eindige element algoritme [5]. In hierdie algoritme word onrealistiese ossilasies in die drukveld selektief gedissipeer, sonder om die res van die veld te beinvloed. Die dissiperende koppelvlak word verkry deur stroomop weegfunksies, wat beheer word deur die karakteristieke rigtings in die vloeiveld, by 'n node. Die algoritme kan dus gebruik word op veranderbare roosters, omdat die dissiperende koppelvlak lokaal beheer word. Die algoritme was toegepas op waterslag probleme waarvan die grenskondisies reservoirs, entpunte, kleppe en pompe ingesluit het. Bevredigende resultate was verkry vir hierdie probleme, al was die geimplementeerde element een-dimensioneel met lineere vormfunksies.

The European Parliment stipulated regulations concerning the forestry vehicles operators' health and working conditions. The allowed whole body vibrations were limited, which influenced the design of the vehicles' cabin. Surveys show a strong correlation between operator's comport and their productivity. The object of the research was Rottne AB Comfort Line Cabin, which was designed to increase the comfort for the forwarder operators. The main objective was to determine the cab's inertia properties, position of the centre of gravity and the resonance frequencies of the cab as well as a system consisting of the cab and its suspension. The methods used were an impact test with Mass-Line Analysis for the cab's properties and Operational Modal Analysis for the system. For both tests a Leuven Measurement System was used, but a part of the calculations were made in parallel by use of a MATLAB code written for this thesis. In addition a suspension test was made to estimate the centre of gravity and it was here treated as the reference value. The authors used reference values and the quality of the obtained results to compare the methods used. Further proposals for future research were made together with hints how to use vibration tests more effectively.