The present thesis involves the study of introducing passive exit flexibility in a two dimensional starting jet. This is relevant to various biological flows like propulsion of aquatic creatures (jellyfish, squid etc.) and flow in the human heart. In the present study we introduce exit flexibility in two ways. The first method was by hinging rigid plates at the channel exit and the second was by attaching deformable flaps at the exit. In the hinged flaps cases, the experimental arrangement closely approximates the limiting case of a free-to-rotate rigid flap with negligible structural stiffness, damping and flap inertia; these limiting structural properties permitting the largest flap openings. In the deformable flaps cases, the flap’s stiffness (or its flexural rigidity EI) becomes an important parameter. In both cases, the initial condition was such that the flaps were parallel to the channel walls. With this, a piston was pushed in a controlled manner to form the starting jet. Using this arrangement, we start the flow and visualize the flap kinematics and make flow field measurements. A number of parameters were varied which include the piston speed, the flap length and the flap stiffness (in case of the deformable flaps). In the hinged rigid flaps cases, the typical motion of the flaps involves a rapid opening with flow initiation and a subsequent more gradual return to its initial position, which occurs while the piston is still moving. The initial opening of the flaps can be attributed to an excess pressure that develops in the channel when the flow starts, due to the acceleration that has to be imparted to the fluid slug between the flaps. In the case with flaps, additional pairs of vortices are formed because of the motion of the flaps and a complete redistribution of vorticity is observed. The length of the flaps is found to significantly affect flap kinematics when plotted using the conventional time scale L/d. However, with a newly defined time-scale based on the flap length (L/Lf ), we find a good collapse of all the measured flap motions irrespective of flap length and piston velocity for an impulsively started piston motion. The maximum opening angle in all these impulsive velocity program cases, irrespective of the flap length, is found to be close to 15 degrees. Even though the flap kinematics collapses well with L/Lf , there are differences in the distribution of the ejected vorticity even for the same L/Lf . In the deformable flap cases, the initial excess pressure in the flap region causes the flaps to bulge outwards. The size of the bulge grows in size, as well as moves outwards as the flow develops and the flaps open out to reach their maximum opening. Thereafter, the flaps start returning to their initial straight position and remain there as long as the piston is in motion. Once the piston stops, the flaps collapse inwards and the two flap tips touch each other. It was found that the flap’s flexural rigidity played an important role in the kinematics. We define a new time scale (t ) based on the flexural rigidity of the flaps (EI) and the flap length (Lf ). Using this new time scale, we find that the time taken to reach the maximum bulge (t* 0.03) and the time taken to reach the maximum opening (t* 0.1) were approximately similar across various flap stiffness and flap length cases. The motion of the flaps results in the formation of additional pairs of vortices. Interestingly, the total final circulation remains almost the same as that of a rigid exit case, for all the flap stiffness and flap lengths studied. However, the final fluid impulse (after all the fluid had come out of the flap region) was always higher in the flap cases as compared to the rigid exit case because of vorticity redistribution. The rate at which the impulse increases was also higher in most flap cases. The final impulse values were as large as 1.8 times the rigid exit case. Since the time rate of change of impulse is linked with force, the measurements suggest that introduction of flexible flaps at the exit could result in better propulsion performances for a system using starting jets. The work carried out in this thesis has shown that by attaching flexible flaps at the exit of an unsteady starting jet, dramatic changes can be made to the flow field. The coupled kinematics of the flaps with the flow dynamics led to desirable changes in the flow. Although the flaps introduced in this work are idealized and may not represent the kind of flexibility we encounter in biological systems, it gives us a better understanding of the importance of exit flexibility in these kinds of flows.

Purpose - This thesis presents a comparison of aircraft design concepts to identify the superior propulsion system model among turbo-hydraulic, turbo-electric and classic jet propulsion with respect to Direct Operating Costs (DOC), environmental impact and fuel burn. --- Approach - A simple aircraft model was designed based on the Top-Level Aircraft Requirements of the Airbus A320 passenger aircraft, and novel engine concepts were integrated to establish new models. Numerous types of propulsion system configurations were created by varying the type of gas turbine engine and number of propulsors. --- Findings - After an elaborate comparison of the aforementioned concepts, the all turbo-hydraulic propulsion system is found to be superior to the all turbo-electric propulsion system. A new propulsion system concept was developed by combining the thrust of a turbofan engine and utilizing the power produced by the turbo-hydraulic propulsion system that is delivered via propellers. The new partial turbo-hydraulic propulsion concept in which 20% of the total cruise power is coming from the (hydraulic driven) propellers is even more efficient than an all turbo-hydraulic concept in terms of DOC, environmental impact and fuel burn. --- Research Limitations - The aircraft were modelled with a spreadsheet based on handbook methods and relevant statistics. The investigation was done only for one type of reference aircraft and one route. A detailed analysis with a greater number of reference aircraft and types of routes could lead to other results. --- Practical Implications - With the provided spreadsheet, the DOC and environmental impact can be approximated for any commercial reference aircraft combined with the aforementioned propulsion system concepts. --- Social Implications - Based on the results of this thesis, the public will be able to discuss the demerits of otherwise highly lauded electric propulsion concepts. --- Value - To evaluate the viability of the hydraulic propulsion systems for passenger aircraft using simple mass models and aircraft design concept.

A shift towards electric and hybrid propulsion within the marine sector create new challenges for conventional water jet units manoeuvred by hydraulic systems. The high efficiency in high speed water jet crafts benefit from being powered by electricity but will be compromised by constantly running hydraulic pumps, draining available electric capacity on-board. Wear and tear on hydraulic components are also an environmental contamination hazard, due to high pressure oil and exposed cylinder rods. However, conventional hydraulic power packs with subsystems to manoeuvre water jet unit is a well proven and reliable marine application.Steer-by-wire is not an uncommon subject, as it is frequently used in several industries such as aviation, automotive and offshore. The purpose of the study is to prepare a concept design proposal with CAD-models and drawings of electrically powered manoeuvring system for Marine Jet Powers DRB 750 steering units. The study did a literature study on the topic and qualitative research to fulfil the purpose. A generic product and concept development is conducted and computer aided design is done to present proposed prototype design.Results from the research gave 4 commercially available electrical actuators, all with significantly different functionality from each other resulting in 4 different concepts and thereof 1 prototype proposal integrated in the waterjet unit according to DNV standards.The selected concept in the study will need some further manufacturing configuration and optimisation for a full installation and working prototype. / Ett skifte mot elektisk och hybriddrift inom marina fartyg och framdrivningssystem skapar nya utmaningar och möjligheter, även så för höghastighetsfartyg där vattenjet har en fördel i sin karaktäristiska höga effektivitet. Idag manövreras vattenjetsaggregat med hjälp av hydraulik, som många gånger drivs med framdrivningsmaskineriet och/eller med en elektisk pump. Dessa system blir en energitjuv i en elektrisk eller hybridlösning för framdrivningen och så saknar det en naturlig lösning på hur en hydraulisk pump ska drivas. Slitage och skador på hydrauliska system kan även leda till miljöfarliga utsläpp av hydraulolja. Framför allt då det handlar om höga hydrauliska tryck och bland annat kolvstänger som är utsatta för påfrestningar från fartygens yttre miljö. Dock är hydrauliska system väl beprövade och pålitliga i marina miljöer.Styrning med hjälp av elkraft är inget som är nytt, även kallat Steer-by-wire, det har gjorts och används inom många områden så som flygplans-, bil- och offshoreindustrin. Syftet med studien är att skapa ett prototypförslag för elektisk manövrering av Marine Jet Powers vattenjetaggregat DRB 750. För att uppnå detta har en litteraturstudie genomförts och kvalitativ forskning för att samla information och få förståelse för ämnet. En generisk product- och konceptutveckling har använts med hjälp av datorstödd konstruktion för att presentera ett prototypförslag.Det har resulterat i 4 koncept med integrerade lösningar från olika tillverkare, som alla skiljer från varandra i funktionalitet och skulle kunna användas på ett sätt för att uppnå målet. Varav ett koncept som valdes, det vidareutvecklades till ett prototypförslag med skruvförband i vattenjetaggregatet och som även sågs till att uppfylla DNV:s standarder och regler. Det valda konceptet behöver vidare utveckling, integrering och optimering för att kunna installeras och testas i fungerande prototyp.

Purpose - This master thesis evaluates the hybrid-electric aircraft project E-Fan X with respect to its economical and environmental performance in comparison to its reference aircraft, the BAe 146-100. The E-Fan X is replacing one of the four jet engines of the reference aircraft by an electric motor and a fan. A turboshaft engine in the cargo compartment drives a generator to power the electric motor. --- Methodology - The evaluation of this project is based on standard aircraft design equations. Economics are based on Direct Operating Costs (DOC), which are calculated with the method of the Association of European Airlines (AEA) from 1989, inflated to 2019 values. Environmental impact is assessed based on local air quality (NOx, Ozone and Particulate Matter), climate impact (CO2, NOx, Aircraft-Induced Cloudiness known as AIC) and noise pollution estimated with fundamental acoustic equations. --- Findings - The battery on board the E-Fan X it is not necessary. In order to improve the proposed design, the battery was eliminated. Nevertheless, due to additional parts required in the new configuration, the aircraft is 902 kg heavier. The turboshaft engine saves only 59 kg of fuel. The additional mass has to be compensated by a payload reduced by 9 passengers. The DOC per seat-mile are up by more than 10% and equivalent CO2 per seat-mile are more than 16% up in the new aircraft. --- Research limitations - Results are limited in accuracy by the underlying standard aircraft design calculations. The results are also limited in accuracy by the lack of knowledge of some data of the project. --- Practical implications - The report contributes arguments to the discussion about electric flight. --- Social implications - Results show that unconditional praise given to the environmental characteristics of this industry project are not justified.

Includes Van Allen thesis (M.S.)--University of Iowa, 1936, and thesis (Ph.D.)--University of Iowa, 1939.