This thesis deals with flow measuring techniques applied on steady and pulsatingflows. Specifically, it is focused on gas flows where density changes canbe significant, i.e. compressible flows. In such flows only the mass flow ratehas a significance and not the volume flow rate since the latter depends onthe pressure. The motivation for the present study is found in the use of flowmeters for various purposes in the gas exchange system for internal combustionengines. Applications can be found for instance regarding measurements of airflow to the engine, or measurements of the amount of exhaust gas recirculation.However the scope of thesis is wider than this, since the thesis aims toinvestigate the response of flow meters to pulsating flows. The study is mainlyexperimental, but it also includes an introduction and discussion of several inindustry, common flow measuring techniques.The flow meters were studied using a newly developed flow rig, designedfor measurement of steady and pulsating air flow of mass flow rates and pulsefrequencies typically found in the gas exchange system of cars and smallertrucks. Flow rates are up to about 200 g/s and pulsation frequencies from 0 Hz(i.e. steady flow) up to 80 Hz. The study included the following flow meters:hot-film mass flow meter, venturi flowmeter, Pitot tube, vortex flowmeter andturbine flowmeter. The performance of these meters were evaluated at bothsteady and pulsating conditions. Furthermore, the flow under both steady andpulsating conditions were characterized by means of a resistance-wire basedmass flow meter, with the ability to perform time resolved measurements ofboth the mass flux ρu, and the stagnation temperature T0.Experiments shows that, for certain flow meters, a quasi-steady assumptionis fairly well justified at pulsating flow conditions. This means that thefundamental equations describing the steady flow, for each instant of time,is applicable also in the pulsating flow. In the set-up, back-flow occurred atcertain pulse frequencies, which can result in highly inaccurate output fromcertain flow meters, depending on the measurement principle. For the purposeof finding means to determine when back flow prevails, LDV measurementswere also carried out. These measurements were compared with measurementsusing a vortex flow meter together with a new signal processing technique basedon wavelet analysis. The comparison showed that this technique may have apotential to measure pulsating flow rates accurately.Descriptors: Flow measuring, compressible flow, steady flow, pulsating flow,hot-wire anemometry, cold-wire anemometry. / QC 20101208

A hybrid FEM/FDM algorithm for particle migration of quasi-steady flow in concentrated suspension materials is proposed in this study. This hybrid FEM/FDM algorithm in which the planar variables, such as pressure field, are described in terms of finite element method, and gapwise variables of temperature, density concentration and time derivatives are expressed by finite difference method. The particle concentration inhomogeneities can be predicted, which is ignored by the existing injection molding simulation packages. Simulation results indicated that powder concentration variation could be significant in practical processing in PIM. / Singapore-MIT Alliance (SMA)

The thesis deals with the development of a new residual error estimator and adaptive algorithms based on the error estimator for steady and unsteady fluid flows in a finite volume framework. The aposteriori residual error estimator referred to as R--parameter, is a measure of the local truncation error and is derived from the imbalance arising from the use of an exact operator on the numerical solution for conservation laws. A detailed and systematic study of the R--parameter on linear and non--linear hyperbolic problems, involving continuous flows and discontinuities is performed. Simple theoretical analysis and extensive numerical experiments are performed to establish the fact that the R--parameter is a valid estimator at limiter--free continuous flow regions, but is rendered inconsistent at discontinuities and with limiting. The R--parameter is demonstrated to work equally well on different mesh topologies and detects the sources of error, making it an ideal choice to drive adaptive strategies. The theory of the error estimation is also extended for unsteady flows, both on static and moving meshes. The R--parameter can be computed with a low computational overhead and is easily incorporated into existing finite volume codes with minimal effort. Adaptive refinement algorithms for steady flows are devised employing the residual error estimator. For continuous flows devoid of limiters, a purely R--parameter based adaptive algorithm is designed. A threshold length scale derived from the estimator determines the refinement/derefinement criterion, leading to a self--evolving adaptive algorithm devoid of heuristic parameters. On the other hand, for compressible flows involving discontinuities and limiting, a hybrid adaptive algorithm is proposed. In this hybrid algorithm, error indicators are used to flag regions for refinement, while regions of derefinement are detected using the R--parameter. Two variants of these algorithms, which differ in the computation of the threshold length scale are proposed. The disparate behaviour of the R--parameter for continuous and discontinuous flows is exploited to design a simple and effective discontinuity detector for compressible flows. For time--dependent flow problems, a two--step methodology is proposed for adaptive grid refinement. In the first step, the ``best" mesh at any given time instant is determined. The second step involves predicting the evolution of flow phenomena over a period of time and refines regions into which the flow features would progress into. The latter step is implemented using a geometric--based ``Refinement Level Projection" strategy which guarantees that the flow features remain in adapted zones between successive adaptive cycles and hence uniform solution accuracy. Several numerical experiments involving inviscid and viscous flows on different grid topologies are performed to illustrate the success of the proposed adaptive algorithms. Appendix 1 Candidate's response to the comments/queries of the examiners The author would like to thank the reviewers for their appreciation of the work embodied in the thesis and for their comments. The clarifications to the comments and queries posed in the reviews are summarized below. Referee 1 Q: The example of mesh refinement for RANS solution with shock was performed with isotropic mesh, while the author claims that it is appropriate with anisotropic mesh. If this is the case, why did he not demonstrate that ? As the author knows well, in the case of full 3--D configuration, isotropic adaptation will lead to substantial grid points. The large mesh will hamper timely turnaround time of simulation. Therefore it would be a significant contribution to the aero community if this point is investigated at a later date. Response: The author is of the view that for most practical situations, a pragmatic approach to mesh adaptation for RANS computations would merely involve generating a viscous padding of adequate fineness around the body and allowing for grid adaptation only in the outer potential region. Of course, this method would allow for grid adaptation in the outer layers of viscous padding only to the extent the smoothness criterion is satisfied while adapting the grids in the potential region. This completely obviates point addition to the wall (CAD surface) and there by avoids all complexities (like loss in automation) resulting from the interaction with the surface modeler while adding point on the wall. This method is expected to do well for attached flows and mildly separated flows. This method is expected to do well even for problems involving shock - boundary layer interaction, owing to the fact that the shock is normal to the wall surface (recall, a flow aligned grid is ideal to capture such shocks), as long as the interaction does not result in a massive separation. This approach has already been demonstrated in section 4.5.3 where in adaptive high-lift computations have been performed. Isotropic adaptation retains the goodness of the zero level grid and therefore the robustness of the solver does not suffer through successive levels of grid adaptation. This procedure may result in large number of volumes. On the other hand, the anisotropic refinement may result in significantly less number of volumes, but the mesh quality may have badly degenerated during successive levels of adaptation leading to difficulties in convergence. Therefore, the choice of either of these strategies is effectively dictated by requirements on grid quality and grid size. Also, it is generally understood that building tools for anisotropic adaptation are more complicated as compared to those required for isotropic adaptation, while anisotropic refinement may not require point addition on the wall. Considering these facts, in the view of the author, this issue is an open issue and his personal preference would be to use isotropic refinement or a hybrid strategy employing a combination of these methodologies, particularly considering aspects of solution quality. Finally, in both the examples cited by the reviewer (sections 6.4.5 & 6.4.6) the objective was to demonstrate the efficacy of the new adaptive algorithm (using error indicators and the residual estimator), rather than evaluating the pros & cons of isotropic and anisotropic refinement strategies. In the sections cited above, the author has merely highlighted the advantages of the refinement strategies in specific context of the problem considered and these statements need not be considered as general. Referee 2 Q: For convection problems, a good error estimator must be able to distinguish between locally generated error and convected error. The thesis says the residual error estimator is able to do this and some numerical evidence is presented, but can the candidate comment how the estimator is able to achieve this ? Response: The ultimate aim of any AMR strategy is to reduce the global error. The residual error estimator proposed in this work measures the local truncation error. It has been shown in the context of a linear convective equation that the global error in a cell consists of two parts--the locally generated error in the cell (which is the R--parameter) and the local error transported from other cells in the domain. Either of these errors are dependent on the local error itself and any algorithm that reduces the local truncation error (sources of error) will reduce the global error in the domain. This conclusion is supported by the test case of isentropic flow past an airfoil (Chapter 3, C, Pg 79), where refinement based on the R--parameter leads to lower global error levels than a global error based refinement itself. Q: While analysing the R--parameter in Section 3.3, the operator δ2 is missing. Response: The analysis in Section 3.3 is based on Eq.(3.3) (Pg 58) which provides the local truncation error. As can be seen from Eq.(3.14), the LHS represents the discrete operator acting on the numerical solution (which is zero) and the first term on the RHS is the exact operator acting on the numerical solution (which is I[u]). Consequently the truncation terms T1 and T2 contribute to the truncation error R1 . However, from the viewpoint of computing the error estimate on a discretised domain, we need to replace the exact operator I by a higher order discrete operator δ2 . This gives the R-parameter, which has contributions from R1 as well as discretisation errors due to the higher order operator, R2 . When the latter is negligible compared to the former, the R--parameter is an estimate of the local truncation error. The truncation error depends on the accuracy of the reconstruction procedure used in obtaining the numerical solution and hence on the discrete operator δ1. On very similar lines, it can be shown that operator δ2 leads to a formal second order accuracy and this operator is only required in computing the residual error estimate. Q: What does the phrase "exact derivatives of the numerical solution" mean ? Response: This statement exemplifies the fact that the numerical solution is the exact solution to the modified partial differential equation and that the truncation terms T1 and T2 that constitute the R--parameter are functions of the derivatives of this numerical solution. Q: For the operator δ2 quadratic reconstruction is employed. Is the exact or numerical flux function used ? Response: The operator δ2 is a higher order discrete approximation to the exact operator I. Therefore, a quadratic polynomial with a three--point Gauss quadrature has been used in the error estimation procedure. Error estimation does not involve issues with convergence associated with the flow solver and therefore an exact flux function has been employed with the δ2 operator. Nevertheless, it is also possible to use the same numerical flux function as employed in the flow solver for error estimation also. Q: The same stencil of grid points is used for the solution update and the error estimation. Does this not lead to an increased stencil size ? Response: In comparison to reconstruction using higher degree polynomials such as cubic and quartic reconstruction, quadratic reconstruction involves only a smaller stencil of points consisting of the node--sharing neighbours of a cell. The use of such a support stencil is sufficient for linear reconstruction also and adds to the robustness of the flow solver, although a linear reconstruction can, in principle, work with a smaller support stencil. A possible alternative to using quadratic reconstruction (and hence a slightly larger stencil) is to adopt a Defect Correction strategy to obtain derivatives to higher order accuracy and needs to be explored in detail. Q: How is the R--parameter computed for viscous flows ? Response: The computation of the R--parameter for viscous flows is on the same lines as for inviscid flows. The gradients needed for viscous flux computation at the face centers are obtained using quadratic reconstruction. The procedure for calculation of the R--parameter for steady flows (both inviscid and viscous) is the step--by--step algorithm in Section 3.5. Q: In some cases, regions ahead of the shock show no coarsening. Response: The adaptive algorithm proposed in this work does not allow for coarsening of the initial mesh, and regions ahead of the shock remain unaffected (because of uniform flow) at all levels of refinement. Q: Do adaptation strategies terminate automatically atleast for steady flows ? Response: The adaptation strategies (RAS and HAS) must, in principle by virtue of construction of the algorithm, automatically terminate for steady flows. In the HAS algorithms though, there are certain heuristic criteria for termination of refinement especially at shocks/turbulent boundary layers. In this work, a maximum of four cycles of refinement/derefinement have only been carried out and therefore an automatic termination of the adaptive strategies were no studied. Q: How do residual--based adaptive strategies compare and contrast with adjoint--based approaches which are now becoming popular for goal--oriented adaptation ? Adjoint--based methods involve solution to the adjoint problem in addition to solving the primal problem, which represents a substantial computational cost. A timing study for a typical 3D problem[2] indicates that the solution of the adjoint problem (which needs the computation of the Jacobian and sensitivities of the functional) could require as much as one--half of the total time needed to compute the flow solution. On the contrary, R--parameter based refinement involves no additional information than that required by the flow solver and is roughly equivalent to one explicit iteration of the flow solver (Section 3.5.1). For practical 3--D applications, adjoint--based approaches will lead to a prohibitively high cost, and more so for dynamic adaptation. This is also exemplified by the fact that there has been only few recent works on 3D adaptive computations based on adjoint error estimation (which consider only inviscid flows)[1,2]. Goal--oriented adaptation involves reducing the error in some functional of interest. This can be achieved within the framework of R--parameter based adaptation, by introducing additional termination criteria based on integrated quantities. Within an automated adaptation loop, such an algorithm would terminate when the integrated quantities do not change appreciably with refinement levels. This is in contrast to the adjoint--based approach which strives to reduce the error in the functional below a certain threshold. Considering the fact that reducing the residual leads to reducing the global error itself, the R--parameter based adaptive algorithm would also lead to accurate estimates of the integrated quantities (which depend on the numerical solution). This is also reflected in the fact that the R--parameter based adaptation for the three--element NHLP configuration predicts the lift and drag coefficients to reasonable accuracy, as shown in Section 4.5.3. The author is of the belief that the R--parameter based adaptive algorithm holds huge promise for adaptive simulations of flow past complex geometries, both in terms of computational cost and solution accuracy. This is exemplified by successful adaptive simulations of inviscid flow past ONERA M6 wing as well as a conventional missile configuration[3]. A more concrete comparison of the R--parameter based and adjoint--based approaches would involve systematically solving a set of problems by both approaches and has not been considered in this thesis. [1] Nemec and Aftosmis,``Adjoint error estimation and adaptive refinement for embedded--boundary cartesian meshes", AIAA Paper 2007--4187, 2007. [2] Wintzer, Nemec and Aftosmis,``Adjoint--based adaptive mesh refinement for sonic boom prediction", AIAA Paper 2008--6593, 2008. [3] Nikhil Shende, ``A general purpose flow solver for Euler equations", Ph.D. Thesis, Dept. of Aerospace Engg., Indian Institute of Science, 2005.

This study aims to investigate variable flow and intermittent flow spray cooling characteristics for efficiency improvement in active two-phase thermal management systems. Variable flow spray cooling scheme requires control of pump input voltage (or speed), while intermittent flow spray cooling scheme requires control of solenoid valve duty cycle and frequency. Several testing scenarios representing dynamic heat load conditions are implemented to characterize the overall performance of variable flow and intermittent flow spray cooling cases in comparison with the reference, steady flow spray cooling case with constant flowrate, continuous spray cooling. Tests are conducted on a small-scale, closed loop spray cooling system featuring a pressure atomized spray nozzle. HFE-7100 dielectric liquid is selected as the working fluid. Two types of test samples are prepared on 10 mm x 10 mm x 2 mm copper substrates with matching size thick film resistors attached onto the opposite side, to generate heat and simulate high heat flux electronic devices. The test samples include: (i) plain, smooth surface, and (ii) microporous surface featuring 100 μm thick copper-based coating prepared by dual stage electroplating technique. Experimental conditions involve HFE-7100 at atmospheric pressure and 30°C and ~10°C subcooling. Steady flow spray cooling tests are conducted at flow rates of 2 - 5 ml/cm².s, by controlling the heat flux in increasing steps, and recording the corresponding steady-state temperatures to obtain cooling curves in the form of surface superheat vs. heat flux. Variable flow and intermittent flow spray cooling tests are done at selected flowrate and subcooling conditions to investigate the effects of dynamic flow conditions on maintaining the target surface temperatures defined based on reference steady flow spray cooling performance.

The main objective of this master thesis is to implement the numerical modelling of the confluence of streams in the Tee-junction using Fluent CFD software. Modelling is carried out for different ratios of flow rates in steady flow. Calculations are evaluated, using a new mathematical model, by curves of loss coefficients. Furthermore, the influence of the selected type of the mesh in geometry on results from numerical modelling of flow is examined. Geometry of the Tee-junction is created in Gambit software. Finally, the results obtained from numerical modelling are confronted with results from an experiment.

In civil and environmental engineering numerous are the applications that require prior collection of data on the ground. When it comes to hydraulic modelling, valuable topographic and morphology features of the region are one of the most useful of them, yet often unavailable, expensive or difficult to obtain. In the last few years UAVs entered the scene of remote sensing tools used to deliver such information and their applications connected to various photo-analysis techniques have been tested in specific engineering fields, with promising results. The content of this thesis aims contribute to the growing literature on the topic, assessing the potentialities of UAV and SfM photogrammetry analysis in developing terrain elevation models to be used as input data for numerical flood modelling. This thesis covered all phases of the engineering process, from the survey to the implementation of a 1D hydraulic model based on the photogrammetry derived topography The area chosen for the study was the Limpopo river. The challenging environment of the Mozambican inland showed the great advantages of this technology, which allowed a precise and fast survey easily overcoming risks and difficulties. The test on the field was also useful to expose the current limits of the drone tool in its high susceptibility to weather conditions, wind and temperatures and the restricted battery capacity which did not allow flight longer than 20 minutes. The subsequent photogrammetry analysis showed a high degree of dependency on a number of ground control points and the need of laborious post-processing manipulations in order to obtain a reliable DEM and avoid the insurgence of dooming effects. It revealed, this way, the importance of understanding the drone and the photogrammetry software as a single instrument to deliver a quality DEM and consequently the importance of planning a survey photogrammetry-oriented by the adoption of specific precautions. Nevertheless, the DEM we produced presented a degree of spatial resolution comparable to the one high precision topography sources. Finally, considering four different topography sources (SRTM DEM 30 m, lidar DEM 1 m, drone DEM 0.6 m, total station&RTK bathymetric cross sections o.5 m) the relationship between spatial accuracy and water depth estimation was tested through 1D, steady flow models on HECRAS. The performances of each model were expressed in terms of mean absolute error (MAE) in water depth estimations of the considered model compared to the one based on the bathymetric cross-sections. The result confirmed the potentialities of the drone for hydraulic engineering applications, with MAE differences between lidar, bathymetry and drone included within 1 m. The calibration of SRTM, Lidar and Drone based models to the bathymetry one demonstrated the relationship between geometry detail and roughness of the cross-sections, with a global improvement in the MAE, but more pronounced for the coarse geometry of SRTM.

Computational fluid dynamics (CFD) modeling is possibly the best available technique in designing and predicting the performance of Stirling and pulse tube refrigerators (PTR). One of the limitations of CFD modeling of these systems, however, is that it requires closure relations for the micro porous materials housed within their regenerators and heat exchangers. Comprehensive prediction of fluid-solid interaction through this media can be obtained only by direct pore level simulation, a process which is time consuming and impractical for system level examination. Through the application of empirical correlations including the Darcy permeability and Forchheimer's inertial coefficient, the microscopic momentum equations governing fluid behavior within the porous structure can be recast as viable macroscopic governing equations. With these constitutive relationships, CFD can be an efficient and powerful tool for system modeling and optimization. The purpose of this study is to determine the hydrodynamic parameters of two mesh fillers relevant to miniature PTRs; stacked screens of 635 mesh stainless steel and 325 mesh phosphor-bronze wire cloth. Experimental setups were designed and fabricated to measure steady and oscillatory pressures and mass flow rates of the working fluid, research-grade helium. Hydrodynamic parameters for the two mesh fillers were determined for steady-state and steady periodic flow in both the axial and radial directions for a range of flow rates, operating frequencies and charge pressures. The effect of average pressure on the steady axial flow hydrodynamic parameters of other common PTR filler materials was also investigated. The determination of sample hydrodynamic parameters and their subsequent computational and experimental methodologies utilized are explained.

Οι καρδιαγγειακές παθήσεις αποτελούν την κύρια αιτία θανάτου στις αναπτυγμένες χώρες. Η στένωση σε μία αρτηρία, είτε αυτή προκαλείται από μία πάθηση όπως το ανεύρυσμα, είτε προκαλείται από μία περίδεση, όπως στις περιπτώσεις των συγγενών καρδιοπαθειών, μπορεί να μεταβάλλει σε σημαντικό βαθμό τα χαρακτηριστικά της ροής του αίματος. Η μελέτη της φυσιολογικής παλλόμενης ροής μέσα από στένωση είναι ιδιαίτερα σημαντική για τη διάγνωση και αντιμετώπιση των αγγειακών νόσων. Το ιατρικό πρόβλημα το οποίο εξετάζουμε στην παρούσα εργασία, είναι η στένωση της πνευμονικής αρτηρίας από περίδεση. Η περίδεση γίνεται προφανώς για να μειωθεί η υψηλή αρτηριακή πίεση και τελικά η ροή του αίματος προς τους πνεύμονες. Πρόκειται για μία χειρουργική μέθοδο αντιμετώπισης συγγενών καρδιοπαθειών. Η περίδεση της πνευμονικής αρτηρίας (pulmonary artery banding - PAB) είτε με συμβατικό τρόπο, ή με την πλέον σύγχρονη μέθοδο μέσω της συσκευής FloWatchTM προκαλεί τη στένωσή της. Με τον συμβατικό τρόπο η στένωση μπορεί να θεωρηθεί αξονικά συμμετρική, ωστόσο με τη χρήση του FloWatchTM είναι μη αξονικά συμμετρική. Έχει αποδειχθεί ότι τόσο η αξονικά συμμετρική, όσο και η μη συμμετρική περίδεση δημιουργεί διαφόρου βαθμού ίνωση του τοιχώματος της πνευμονικής αρτηρίας. Η αναδόμηση της πνευμονικής αρτηρίας είναι πολύ ηπιότερη στην περίπτωση της περίδεσης με το FloWatchTM. Η διαφοροποίηση αυτή έγκειται κυρίως στο ότι η συμβατική περίδεση προκαλεί για συγκεκριμένη μείωση της διατομής ισχυρότερη μείωση της περιμέτρου της διατομής από εκείνης της περίδεσης με το FloWatchTM. Στην παρούσα εργασία γίνεται αναφορά και ανάλυση των διαφόρων περιπτώσεων ροής σε στενώσεις αρτηριών, των συγγενών καρδιοπαθειών και των τεχνικών περίδεσης της πνευμονικής αρτηρίας. Επιπρόσθετα, μελετήθηκαν και υπολογίστηκαν η μόνιμη και η παλλόμενη ροή σε αξονικά συμμετρική 25% στένωση προκαλούμενη από συμβατική περίδεση, καθώς και η μόνιμη και παλλόμενη ροή σε μη συμμετρική 25% στένωση της πνευμονικής αρτηρίας όπως προκαλείται από το FloWatchTM, μέσω των πακέτων Fluent και Gambit. Η υπολογιστική μελέτη του πεδίου ροής περιλαμβάνει την κατανομή ταχυτήτων, τον προσδιορισμό των περιοχών ανακυκλοφορίας, την κατανομή των πιέσεων και την σύγκριση των παραπάνω μεγεθών με τα αντίστοιχα αποτελέσματα της βιβλιογραφίας. Τέλος, με βάση τα αποτελέσματα γίνεται η σύγκριση των δύο μελετούμενων μεθόδων περίδεσης. Αριθμητικά ρεαλιστικά δεδομένα ελήφθησαν από την καρδιοχειρουργική κλινική του νοσοκομείου Παίδων «Αγία Σοφία». / Cardiovascular diseases are the leading cause of death in developed countries. A stenosis in an artery , caused either by a disease such as an aneurism or by a banding (such as in congenital diseases) can change the characteristics of the blood flow very seriously. The study of the physiological pulsatile flow through a stenosis is very important for the diagnosis and treatment of the arterial diseases. The medical problem which is examined in this study is pulmonary artery stenosis caused by a banding. The banding takes place to reduce the high arterial pressure and finally the blood flow from the heart to the lungs. It is a surgical method used for treatment of congenital heart diseases. The pulmonary artery banding either with the use of the conventional method or the most modern with the use of the FloWatchTM technology causes stenosis of the artery. With the conventional method, stenosis can be considered axially symmetrical while with the use of FloWatchTM it is asymmetrical. It has been proven that both the axially symmetrical and asymmetrical banding cause fibrosis of the pulmonary artery walls of different degrees. The reconstruction of the pulmonary artery is milder where there is banding with FloWatchTM. This differentiation is based mainly on the fact that the conventional banding causes, for a specific decrease of the cross-section, a decrease in the perimeter of the cross-section higher than that of banding with FloWatchTM. In this assignment there is a report of different cases of flow in arterial stenosis, in congenital heart diseases and pulmonary banding techniques. In addition what was studied and appreciated was the steady and pulsatile flow in axially symmetrical 25% stenosis caused by the conventional banding, as well as the steady and pulsatile flow in asymmetrical 25% stenosis of pulmonary artery caused by FloWatchTM with the use of Fluent and Gambit. The numerical study of flow distribution includes velocity distribution, designation of back flow area, distribution of pressure and comparison of these quantities with the results in bibliography. Finally, based on the results, there is a comparison of the two banding methods under study. The numerical realistic data were received from the cardio-surgical clinic of children’s hospital “Aghia Sophia”.

This master’s thesis is divided into two logical parts. The first part contains theory of calculation of steady state and short-circuits conditions within 110 kV distribution network. Newton’s method and short-circuit current calculation is also explained here. It also deals with classification and aftereffects of transient performance occurring in power networks. The second part contains practical calculation of steady flow and short-circuit conditions at parallel operation of transformers T403 and T402 in 400/110 kV transformer stations Sokolnice and Otrokovice. This calculation is done with program used by system operators called SINAUT Spectrum and consequently analyzed. This part also contains brief description of substations from this region.

The thesis is concerned with an appraisal of capacity of channel and design of suitable measures for environmental protection. Solved segment is located in the channel of Český potok in RK 0,000 – 6,366. The channel is flowing through villages of Čelechovice na Hané, Smržice a Držovice in solved segment. Within own solution the locality was divided into three partial sections, which is enabling clearer description of the proposed measures. Flood measures are proposed in several variants for each partial section. Calculations of flow capacity and water surface for the selected N-year flows were performed by using the program of HEC - RAS 4.1.0. Proposed solutions to flood measures are processed in the drawings documentation.