The emergence of closed-loop Brayton cycle power plants, such as the PBMR, resulted in the need to simulate start-up transients for industrial multi-stage axial flow compressors operating at subsonic conditions. This implies that the delivery pressure and power requirements must be predicted for different mass flow rates and rotational speeds while operating in the first and fourth quadrants on the compressor performance charts. Therefore, an analytical performance prediction model for subsonic multi-stage axial flow compressors had to be developed that can be integrated into a generic network analysis software code such as Flownex. For this purpose, performance calculations based on one-dimensional mean-line analysis demonstrated good accuracy, provided that the correct models for losses, incidence and deviation are used. Such a model is therefore the focus of this study. A preliminary analytical performance prediction code, with the capability of interchanging between different deviation and loss models is presented. Reasonably complex loss models are integrated in association with the correct incidence and deviation models in a software package called "Engineering Equation Solver" (EES). The total pressure loss calculations are based on a superposition of theoretically separable loss components that include the following: blade profile losses, secondary losses and annulus losses. The fundamental conservation equations for mass, momentum and energy for compressible "rotating pipe" flow were implemented into the performance prediction code. Performance prediction models were validated against experimental data and evaluated according to their ease of implementation. Verification was done by comparing simulation results with experimental work done by Von Backstrom. This includes a calculation to determine the uncertainty in the experimental results. Furthermore, since the conventional definition of isentropic efficiency breaks down at the boundaries of quadrants on the performance charts, a new non-dimensional power formulation is presented that allows for the calculation of the compressor power in all of the relevant quadrants. Good comparison was found between simulation results and measurements in the first and fourth quadrant of operation. / Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2007.

Thesis (M.App.Sc.) - Carleton University, 2005. / Includes bibliographical references (p. 174-179). Also available in electronic format on the Internet.

Thesis (Ph.D.)--Mississippi State University. Department of Aerospace Engineering. / Title from title screen. Includes bibliographical references.

Thesis (Ph.D)--Aerospace Engineering, Georgia Institute of Technology, 2010. / Committee Chair: Dr. Lakshmi N. Sankar; Committee Member: Dr. Alex Stein; Committee Member: Dr. J.V. R. Prasad; Committee Member: Dr. Richard Gaeta; Committee Member: Dr. Suresh Menon. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Le développement de machines à forte vitesse spécifique et de taille réduite en régime subsonique suscite actuellement une forte demande dans de nombreux domaines industriels. Les machins à rotors contrarotatifs largement étudiées en aéronautique constituent une alternative efficace aux machines conventionnelles offrant de nombreux avantages : réduction de la vitesse de rotation, de l'encombrement radial et une grande flexibilité d'utilisation. Cependant, leur utilisation dans des applications subsoniques courantes nécessite une meilleure compréhension de leur fonctionnement et notamment de l'interaction inter-rotors pour mieux les concevoir. Ce travail a pour objectif d'étudier et de caractériser expérimentalement un étage contrarotatif fonctionnant en conduit, conçu avec le code de conception et d'analyse pour rotor et rotor-stator, MFT auquel on a implémenté une méthode de conception simple et rapide pour dessiner le rotor aval. On analyse en particulier l'effet de la distance axiale entre les rotors et l'effet du rapport de leur vitesse. Il met en évidence une nette amélioration des caractéristiques et du rendement global par rapport à une machine conventionnelle. Par ailleurs, plusieurs aspects de l'interaction entre les rotors sont constatés à travers des mesures locales à proximité des rotors. Le présent mémoire s'articule autour de quatre parties : conception d'un étage rotor-stator et d'un étage contrarotatif ; conception du dispositif expérimental normalisé, AERO²FANS pour les mesures de performances globales et locales instationnaires ; caractérisation et comparaison des deux étages et validation de la conception de MFT; enfin, étude des effets de la distance axiale et du rapport des vitesses sur les performances globales et locales. / Recently, the need for smaller axial fans with high specific speeds lead to the design of counter-rotating axial fans. The design of this kind of machines, which have promising aerodynamic performances, suffers from a lack of knowledge about their aerodynamics. Counter-rotating rotors, widely studied in aeronautics, are an effective alternative to conventional machines and offer many advantages: rotation ratio and diameter reduction, and high flexibility in use. However, a better understanding of their working and of the rotors interaction is required to enhance their design and to make them widely integrated in current applications. This experimental research work investigates on a ducted counter-rotating stage designed with a home code, MFT based on an inverse design method for rotors and rotor-stator stages, and to which a rapid and simple method is implemented to design the rear rotor. The study focuses on the effects of the rotation ratio and on the axial spacing between rotors. It highlights several aspects of the rotors interaction through global performance and local unsteady measurements. This dissertation is organized in four parts: rotor-stator and rotor-rotor stages design; design of the experimental facility, AERO²FANS allowing global performance and local unsteady measurements; comparison between the two stages and design validation; investigation on the effects of the rotation ratio and the axial spacing on the global and the local performances.

The dynamic response of the compression system is a key factor in determining the operability characteristics of an aircraft gas turbine engine subjected to various transient environmental and control inputs. Computer models have been developed to simulate this response. The primary inputs to these models are the wide-range, steady-state compressor stage characteristics. To reduce the dependence of these dynamic models on experimental performance data, significant effort has been devoted to the development of stage characteristic prediction techniques. As part of this ongoing effort, a model to simulate rotating stall inception and development in axial-flow compressor stages was constructed. This model was applied to an isolated rotor build to investigate the sensitivity of the predicted stall behavior to the shape of the high-incidence portions of the blading relative total pressure loss and turning angle characteristics, as well as to the rotor speed. In addition, the predicted steady-state, stalled rotor performance was compared with corresponding low-speed, experimental data. By superimposing small flow perturbations on the rotor flow field over a range of initial operating conditions, it was demonstrated that stall inception occurs only for initial relative flow incidence near some critical value, defined as the incidence for which the relative total pressure losses incurred in the blade passage increase sharply. For initial operating points away from the critical one, no propagating disturbance was predicted. Also, a strong sensitivity of the predicted stall behavior to the shape of the high-incidence portion of the relative total pressure loss characteristic was observed with increased-slope curves resulting in earlier stall inception and larger amplitude stall disturbances. The effect of increased-slope loss curves on the predicted steady-state rotor performance was to cause a more abrupt drop in the flow and total pressure rise coefficients at the stall limit. Comparatively, varying the shape of the turning angle characteristic or the rotor speed had only a slight effect on the simulated rotating stall phenomena. Finally, the predicted install total pressure characteristic for a selected low-speed case was compared with experimental data with favorable results. / Master of Science

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Axial flow fans used in large-scale air-cooled steam condensers (ACSCs) may operate under distorted inflow conditions. These conditions occur due to the prevailing wind conditions, the presence of buildings, and the location of the fan within the ACSC. Fans located on the periphery of the ACSC are affected the most due to their exposure to strong winds and the inner fans drawing in air past them. Distorted inflow conditions cause varying fan blade and gearbox loading conditions. The purpose of the investigation was to simultaneously measure the inlet air flow and the resultant blade and gearbox loading conditions of a single fan located on the periphery of a large-scale ACSC. Inlet and heat exchanger bundle outlet air flow velocities were measured using a combination of ultrasonic and propeller anemometers while blade loading was measured with strain gauges attached at the neck of the specific blade being monitored. Strain gauges were also attached to the low-speed fan shaft to measure gearbox loading. Measurements were recorded over a period of 8 days where it was found that increased wind resulted in increased air flow in the axial direction of the fan, which then caused a reduction in average blade loading. This was due to a decreased static pressure rise over the fan. The fan blade was found to vibrate at its own natural frequency of 6 Hz when excited by the variable aerodynamic loading. The aerodynamic loading was extracted from the measured data and was found to correlate well with previous experimental work performed by Bredell et al. (2006a). Shaft bending stresses and torque were found to oscillate at the fan’s rotational frequency of 2Hz with a large torque exerted on the shaft during fan start-up. / AFRIKAANSE OPSOMMING: Aksiaalvloeiwaaiers wat by groot lugverkoelde stoomkondensors gebruik word, werk dikwels onder verwronge inlaat lugvloei toestande wat geskied as gevolg van heersende winde, die teenwoordigheid van geboue en die posisie van die waaier in die kondensor. Waaiers wat geleë is op die rand van die kondensor word die meeste beïnvloed as gevolg van blootstelling aan die sterk winde en dwarsvloei wat deur die binneste waaiers geïnduseer word. Verwronge inlaat lugvloei veroorsaak gevolglik variërende waaierlem en ratkas belastingstoestande. Die doel van hierdie ondersoek was om terselfdetyd die inlaat lugvloei asook waaierlem en ratkas belastingstoestande van ’n enkele waaier wat op die rand van ’n grootskaalse lugverkoelde stoomkondensor geleë is, te meet. Waaier inlaat en warmteruiler uitlaat lugvloei snelhede is gemeet met ’n kombinasie van ultrasoniese- en skroefwindsnelheidsmeters terwyl die lem en ratkas belastings gemeet is met rekstrokies. Metings is oor ’n tydperk van 8 dae geneem. Die bevindinge toon dat ’n toename in windsnelheid ’n toename in aksiale lugvloei tempo, deur die waaier veroorsaak. ’n Afname in die gemiddelde lembelasting is waargeneem as gevolg van ’n afname in die waaier statiese druk. Daar is ontdek dat die waaierlem teen ’n natuurlike frekwensie van 6 Hz vibreer wanneer dit opgewek word deur die wisselende aerodinamiese belasting. Die aerodinamiese belasting is verkry uit die gemete data en vergelyk goed met die numeriese werk van Bredell et al. (2006a). Daar is ook bevind dat waaier-as buigspannings en wringkragte ossileer teen die waaier se rotasiefrekwensie van 2Hz met ’n groot wringkrag wat op die as uitgeoefen word wanneer die waaier aangeskakel word. iii

Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The majority of power stations in South Africa are located in coal rich, but arid regions where wet-cooled condenser systems are not feasible from an environmental and economic perspective. Consequently the focus on power generation cooling has shifted towards dry-cooling systems using air-cooled steam condensers (ACSC). The steam passing through the ACSC units is cooled by an air-draught, mechanically induced by large diameter axial flow fans. Consequently the effectiveness of the cooling is impacted by the performance of these fans, which ultimately affects the overall efficiency of the power plant. However, due to the large diameters (> 10 m) of these fans, their performance is predicted based on small scale test results using the fan scaling laws. The objective of this project was to develop a methodology which accurately predicts the fan performance of more than one fan configuration using computational fluid dynamics (CFD) software and validating the results with experimental tests. Four fans were considered in this study of which three were scaled fan models of large air-cooled axial fans. The performance of the scaled fan models (L1-, L2- and N-fan) were measured in a type A, BS 848 standard fan test facility. The geometries of the fans were scanned three-dimensionally to obtain the models for simulation purposes. The other fan considered was an 8- bladed axial fan designed by Bruneau (1994) and referred to as the B-fan. Simulations were carried out for the L2-, N- and B-fan for different computational domains while implementing the multiple reference frames (MRF) and steady RANS approach. Three variations of the k-ε turbulence model were also investigated. Noticeable differences were found between the experimental and numerical results of the B-fan. Good correlations between the numerical and experimental fan static pressure, fan power and fan static efficiency were found for the two scaled model fans over a large operating range. The performance of the full scale fans, however, did not correlate well with the performance of the scaled models. It is concluded that accurate simulations of axial fans are possible although these domains require a large number of mesh elements. It is recommended that further research is carried out to investigate the relationship between full scale and small scale fan models. / AFRIKAANSE OPSOMMING: Die meerderheid steenkool kragstasies in Suid-Afrika is geleë in droë, maar steenkool ryke streke waar natverkoelde kondensor stelsels uit ʼn omgewings en ekonomiese perspektief nie geskik is nie. Die fokus in kragopwekking verkoeling het dus verskuif na droë-verkoelings stelsels en spesifiek die gebruik van lugverkoelde stoomkondensors (LVSKs). Die stoom in LVSK eenhede word verkoel deur atmosferiese lug wat meganies geïnduseer word deur groot aksiaalvloeiwaaiers. Die effektiwiteit van die verkoelingsproses word gevolglik beïnvloed deur die werksverrigting van hierdie waaiers wat uiteindelik die algehele effektiwiteit van die kragstasie beïnvloed. As gevolg van hierdie waaiers se grootte word hulle werksverrigting egter bepaal op grond van kleinskaal toetsresultate en deur gebruik te maak van die waaierskaleringswette. Die hoofdoelwit van hierdie projek was om ‘n metodiek te ontwikkel wat die werksverrigting van ʼn aksiaalwaaier akkuraat kan voorspel vir ʼn verskeidenheid opstellings, deur gebruik te maak van berekenings vloei meganika (BVM) sagteware en die resultate eksperimenteel te verifieer. Die projek het vier waaiers ondersoek waarvan drie van hierdie waaiers geskaleerde modelle van groot lugverkoelde aksiaalwaaiers was. Die werksverrigting van die geskaleerde waaiers (L1-, L2- en N-waaier) was met ‘n tipe A, BS 848 standaard waaier toetsfasiliteit gemeet. Die geometrie van dié waaiers was ook drie-dimensioneel opgemeet vir simulasie doeleindes. Die B-waaier, ‘n 8 lem aksiaalwaaier, wat ontwerp is deur Bruneau (1994) was slegs numeries ondersoek. Die L2-, N- en Bwaaier was gesimuleer in verskillende berekeningsdomeine deur gebruik te maak van die multi verwysingsraamwerk en gestadigde vloeiberekenings benaderings. Drie k-ε turbulensie modelle was ook ondersoek. Merkbare verskille tussen die eksperimentele en numeriese resultate van die Bwaaier was waargeneem. Goeie korrelasie tussen die eksperimentele en numeriese resultate van die geskaleerde waaiers vir ‘n wye bedryfsbestek was gevind. ‘n Vergelyking tussen die volskaal en kleinskaal waaiers se werksverrigting het egter beduidende afwykings aangetoon. Deur gebruik te maak van ‘n groot aantal selle in die berekeningsdomein was dit moontlik om ʼn verskeidenheid aksiaalvloeiwaaiers akkuraat te simuleer. Verdere navorsing wat die verhouding tussen volskaal en kleinskaal waaiers ondersoek woord aanbeveel.

Thesis (PhD)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Axial flow fan arrays form part of air-cooled steam condensers in direct drycooled power plants. This dissertation investigates the performance of axial flow fans when located at the perimeter of a fan array. The perimeter (or edge) fans may experience a reduction in air flow through the fan due to the prevalence of distorted inlet conditions upstream of the fan. The reduction in air flow leads to a reduction in the heat transfer capability of the steam condenser and a consequent reduction in the electricity output of the power plant. Due to the physical size of an air-cooled condenser, full-scale experiments are often impractical and computational fluid dynamics (CFD) is used to model its performance under various conditions. To limit the size of the CFD model the axial flow fans in the CFD analysis are represented by means of simplified methods. Three different simplified methods are presented and applied to a CFD model of a single axial flow fan, namely the pressure jump method (PJM), actuator disc method (ADM) and extended actuator disc method (EADM). The results are compared to experimental values. The comparison highlights the limitations of the models: The ADM fails to model fan performance correctly at low flow rates, while the PJM ignores the variation in fan blade properties at different locations within the fan rotor. The EADM is presented as an improvement on both the other two models. A multiple fan test facility is constructed, consisting of three 630 mm diameter fans extracting air from a common inlet chamber. The inlet chamber is constructed in such a way that one of the three fans act as the perimeter (edge) fan. The floor of the inlet chamber can be adjusted to increase or reduce the inlet flow distortion experienced by the edge fan. Six different fan configurations are tested in the position of the edge fan and an empirical method is derived by which the volumetric effectiveness of an edge fan can be predicted. The experimental results are compared to CFD results for the same facility using the three different simplified simulation methods investigated previously. Particle image velocimetry (PIV) measurements are also performed upstream of the edge fan and the velocity profiles at the inlet of the fan are compared to the profiles obtained numerically. The comparisons show that the EADM predicts the performance of the edge fan more accurately than the ADM en PJM. The effect of adding a walkway and removing the bell mouth upstream of the edge fan was investigated using the EADM. The results are used to show the location of the loss mechanisms upstream of the edge fan. The addition of a walkway moves the location of the pressure loss away from the edge fan bell mouth towards the edge of the walkway. Consequently the distortion directly upstream of the edge fan is reduced and its volumetric effectiveness increased. The effect of removing the edge fan’s bell mouth is similar to the effect of adding a walkway upstream of the edge fan. / AFRIKAANSE OPSOMMING: Aksiaalwaaiermatrikse vorm deel van lugverkoelde kondensors in direk droëverkoelde kragstasies. Hierdie verhandeling ondersoek die werkverrigting van aksiaalwaaiers wat geleë is op die rand van ‘n groot waaiermatriks. Die randwaaiers kan ’n vermindering in deurvloei ondervind as gevolg van versteurde inlaattoestande stroom-op vanaf die waaier. Die vermindering in lugvloei lei tot ’n vermindering in die warmetoordagvermoë van die stoomkondensor en ’n gepaardgaande afname in die elektrisiteitslewering van die kragstasie. As gevolg van die fisiese grootte van die lugverkoelde kondensor is volskaalse eksperimente gewoonlik onprakties en word berekeningsvloeimeganika (BVM) gebruik om die werking van die aanleg onder verskeie toestande te modelleer. Ten einde die grootte van die BVM model te beperk, word die aksiaalwaaiers in so ‘n BVM analiese voorgestel met behulp van vereenvoudigde metodes. Drie verskillende vereenvoudigde metodes word aangebied en toegepas op ‘n BVM model van ‘n enkelwaaier, naamlik die druksprongmetode, die aksieskyfmetode en die verlengde aksieskyfmetode. Die resultate word vergelyk met eksperimentele waardes. Die vergelyking benadruk die beperkings van die modelle: Die aksieskyfmetode kan nie die werking van die waaier akkuraat voorspel by lae vloeie nie en die druksprongmetode ignoreer die variasie in lemeienskappe op verskillende liggings binne-in die waaierrotor. Die verlengde aksieskyfmetode word voorgestel as ‘n verbetering op die ander twee metodes. ‘n Veelvuldige waaiertoetsfasiliteit is saamgestel, bestaande uit drie 630 mm deursnee waaiers wat lug uit ’n gemeenskaplike inlaatkamer suig. Die inlaatkamer is so saamgestel dat een van die waaiers in die fasiliteit ‘n randwaaier verteenwoordig. Die vloerhoogte van die inlaatkamer kan aangepas word om die inlaatversteuring wat deur die raandwaaier ondervind word te vermeerder of te verminder. Ses verskillende waaierkonfigurasies is getoets in die randwaaierposisie. ‘n Empiriese metode waarmee die volumetriese effektiwiteit van ‘n randwaaier voorspel kan word is afgelei. Die eksperimentele resultate word vergelyk met ooreenstemmende BVM resultate vir dieselfde fasiliteit deur gebruik te maak van die drie verskillende vereenvoudigde metodes wat vroeër ondersoek is. Partikelbeeld snelheidsmetings word ook stroom-op vanaf die randwaaier uitgevoer en die snelheidsprofiele by die inlaat van die waaier word vergelyk met profiele wat numeries bereken word. Die vergelykings wys dat die verlengde aksieskyfmetode die werkverrigting van ’n aksiaalwaaier meer akkuraat voorspel as die aksieskyf- of druksprongmetodes. Die effek van die installering van ‘n loopvlak en die verwydering van die randwaaier se inlaatmondstuk word ondersoek met behulp van BVM deur gebruik te maak van die verlengde aksieskyfmetode. Die resultate word spesifiek gebruik om die ligging van die verliesmeganismes stroom-op vanaf die randwaaier aan te dui. Die resultate wys dat die installering van ‘n loopvlak die ligging van die drukverlies wegneem vanaf die rand van die waaierinlaat na die rand van die loopvlak. Dit verminder die inlaatversteuring stroom-op vanaf die randwaaier en die volumetriese effektiwiteit word verhoog. Die verwydering van die randwaaier se inlaatmondstuk het ‘n soortgelyke effek as die installering van ‘n loopvlak stroom-op vanaf die randwaaier.

Thesis (PhD (Mechanical Engineering))--University of Stellenbosch, 1990. / Leaves printed on single pages, preliminary pages i- viii and numbered pages 1-1-R5. Includes bibliography, list of tables and figures and list of appendices. Digitized at 330 dpi black and white PDF format (OCR),using KODAK i 1220 PLUS scanner. / ENGLISH ABSTRACT: A numerical procedure for predicting the effect of inlet flow distortions on the performance of axial flow fans is proposed. The study is aimed specifically at fans of low solidity and low hub-to-tip ratios, which have attained some importance with the advent of large directly air-cooled power stations in certain arid regions of the world. The numerical model is an extension to cylindrical polar coordinates of the SIMPLEN algorithm that has been developed by the author previously. The algorithm is implemented in a computer code, FLOVAX, which solves the incompressible Navier-Stokes equations, augmented by the k-Ɛ model of turbulence, on a computational domain that is aligned with the cylindrical polar coordinate system. Several relatively simple flow problems are solved to verify the code: laminar stagnation flow, laminar flow near a rotating disk, turbulent flow near a propeller, turbulent flow through an abrupt axisymmetric expansion, and turbulent swirling flow in an annulus. Good agreement is obtained between the numerical solutions and the corresponding analytical, empirical or published experimental and numerical results. Some experimental results are also presented: measurements of shaft power, volume flow rate and static pressure rise were taken in a setup comprising an axial flow fan mounted in the wall of a wind tunnel. The wind tunnel was used to provide flow across the fan intake, thus establishing distorted inflow conditions. Detailed measurements of the velocity and static pressure distributions in the duct downstream of the fan rotor were also performed. It is clear from the results that flow across the intake of the test fan has a detrimental effect on its performance in that an increased amount of power is necessary to deliver the same flow rate as with no crossflow. In the numerical predictions, blade element theory is used to model the thrust and torque exerted by the fan blades on the air. The numerical results generally confirm the results of the experiment, although the increase in power is underestimated: an increase of only approximately half of the measured increase is predicted. Several recommendations for improvement of the numerical procedure are made. / AFRIKAANSE OPSOMMING: 'n Numeriese prosedure vir die voorspelling van die invloed van versteurings in inlaatvloei op die werking van aksiaalwaaiers word daargestel. Die studie is spesifiek gemik op waaiers van lae soliditeit en lae lempunt-tot-naafverhoudings. Waaiers van hierdie tipe het belangrikheid verwerf sedert die onlangse totstandkoming van groot lugverkoelde kragstasies in sekere droe werelddele. Die numeriese model is 'n uitbreiding na silindriese poolkoordinate van die SIMPLEN-algoritme wat voorheen deur die skrywer ontwikkel is. Die algoritme word geimplementeer in 'n rekenaarkode, FLOVAX, wat die onsamedukbare Navier-Stokes-vergelykings, aangevul deur die k-Ɛ-turbulensiemodel, oplos op 'n berekeningsgebied wat saamval met die silindriese poolkoordinaatstelsel. Verskeie relatief eenvoudige vloeiprobleme word opgelos ter verifikasie van die kode: laminere stagnasievloei, laminere vloei op 'n roterende skyf, turbulente vloei deur 'n propeller, turbulente vloei deur 'n aksiaalsimmetriese vernouing, en turbulente roterende vloei in 'n annulus. Goeie ooreenstemming tussen die numeriese oplossings en die ooreenstemmende analitiese, empiriese of gepubliseerde eksperimentele en numeriese resultate is verkry. Eksperimentele resultate word ook aangebied: metings van asdrywing, volumevloei en statiese drukstyging is geneem in 'n opstelling wat bestaan het uit 'n aksiaalwaaier wat in die wand van 'n windtonnel gemonteer is. Die windtonnel is gebruik om versteurde-invloei-toestande te genereer in die vorm van dwarsvloei oor die waaier-inlaat. Snelheids- en statiese drukverdelings in die kanaal stroom-af van die waaierrotor is ook gemeet. Dit blyk duidelik uit die resultate dat die dwarsvloei oor die inlaat van die toetswaaier 'n nadelige uitwerking het op die werking daarvan in die opsig dat meer drywing nodig is om dieselfde vloeitempo te handhaaf as wat die geval is sonder dwarsvloei. Vir die numeriese voorspellings word van lem-element-teorie gebruik gemaak om die stukrag en draaimoment wat deur die waaier op die lug uitgeoefen word, te modelleer. Die numeriese resultate bevestig oor die algemeen die eksperimentele resultate, alhoewel die drywingstoename onderskat word met sowat die helfte van die gemete toename. Verskeie aanbevelings ter verbetering van die numeriese prosedure word gemaak.