An aircraft may experience inlight ice accretion and corresponding reductions in performance and control when the vehicle encounters clouds of super-cooled water droplets. In order to study anti-icing coatings, the EADS-IW Surface Engineering Group is building a refrigerated wind tunnel. Several variations of droplet delivery systems were explored to determine the most effective way to introduce mono-dispersed droplets into the wind tunnel. To investigate this flow, timeurate, unsteady viscous flow simulations were performed using the Loci/CHEM flow solver with a multi-scale hybrid RANS/LES turbulence model. A Lagrangian droplet model was employed to simulate the movement of water droplets in the wind tunnel. It was determined that the droplet delivery system required pressure relief to properly orient the flow inside the droplet delivery tube. Additionally, a streamlined drop tube cross-section was demonstrated to reduce turbulence in the wake and decrease the variability in droplet trajectories in the test section.

No description available.

No description available.

No description available.

År 2008 inleddes bygget av den 6 kilometer långa tunneln Citybanan som sträcker sig genom stora delar av centrala Stockholm. Tunneln utgörs till största del av bergtunnlar men även av betongtunnlar på ett antal kortare sträckor. Syftet med tunneln är att avlasta spårtrafiken i Stockholm genom att fördubbla spårkapaciteten. Hela pendeltågstrafiken kommer omdirigeras till tunneln och de två nya pendeltågsstationerna Stockholm City och Odenplan kommer att byggas. Svårigheterna med tunnelbyggandet beror på det grundvatteninläckage som sker till bergtunneln genom bergets sprickor och svaghetszoner. Ett högt inläckage kan leda till att grundvattennivån sänks och jordlager ovanför tunneln krymper. Det kan leda till  förändringar i den ovanliggande stadsmiljön och kostsamma sättningsskador. På grund av Stockholms geologiska heterogenitet och befintliga konstruktioner krävs försiktighet och korrekta åtgärder för att minimera de kostsamma konsekvenserna. För att minimera sättningarna har Trafikverket, som har huvudansvaret för Citybanan, utfört prediktioner av inläckaget till de olika delsträckorna i tunneln. Prediktionerna är baserade på undersökningar om den geologiska strukturen och antaganden om vilka tätningsåtgärder som ska utföras. Därefter har Miljödomstolen bestämt vilka värden som beviljats för de olika sträckorna som Trafikverket måste anpassa sig efter. För att sammanställa prediktionerna,  de begränsande värdena och det verkliga inläckaget har data hämtats från utredningsdokument utförda på beställning av Trafikverket, miljödomar och Trafikverkets mätdatabas för omgivningspåverkan (TMO). Inläckaget har överskridit de tillåtna gränsvärdena till de två arbetstunnlarna Torsgatan och Norra station. Arbetstunnlarna ligger i närheten av sättningskänsliga områden, där framförallt området kring Stockholm City, till följd av inläckaget kan ha fått en förhöjd risk. Till de andra delsträckorna har inläckaget varit lägre än de högsta tillåtna värdena. Inläckaget har på fem sträckor överskridit de initiala prediktionerna. Miljödomarnas gränsvärden har, på alla delsträckor utom en, fastställts högre än prediktionerna. På grund av Stockholmsområdets geologiska komplexitet och de sättningskänsliga områdena bör det sättas ifråga om de tillåtna värdena bör sättas lägre för att stimulera Trafikverket att minimera inläckaget och således grundvattenpåverkan. / Construction of the 6 kilometres long tunnel Citybanan was initiated in 2008 by The Swedish Transport Administration. The majority of the tunnel consists of rock tunnels, but some shorter parts are concrete tunnels. The main purpose of the tunnel is to double the rail traffic capacity of central Stockholm and absorb commuter traffic. In addition to this, two new commuter train stations have been constructed. Cracks and weak zones within the rock is a challenge that can result in issues such as groundwater leakage. High groundwater leakage can cause the surrounding groundwater levels to sink which can lead to soil compaction around the tunnel. Soil compaction can  cause land subsidence and further on damage buildings and existing infrastructure. Due to the heterogenic geology in Stockholm, and the vast amount of existing structures, specific actions have to be taken to minimize the risk of unwanted effects. Predictions has been done by The Swedish Transport Administration regarding the groundwater leakage in the different parts of the tunnel. The predictions are based on the geological structure and the planned amount of made grouting operations. Later, the Environmental court decided the allowed amount of groundwater leakage in the different sections. The predictions, permissions and actual inleakage presentet in this report have been retrieved from the Environmental Impact Assessment, the court verdicts and the Transports Administration database for environmental impact (TMO). The inleakage has exceeded the allowed amount into the two work tunnels Torsgatan and Norra station. These sections are located near sensitive areas, which can lead to an  increased risk of subsidence damage. In total, the leakage has exceeded the predicted values in five different sections. The allowed inleakage is higher than the predicted inleakage at all sections except for one. Due to the complex geology and the risk of subsidence in central Stockholm, this report questions whether the allowed leakage should have been as high as they were. Lowering the level  of  accepted  leakage  could  potentially  stimulate  the  Transport  Administration  to minimize the leakage and thus the undesirable side effects.

An  important  task   during  the  construction  process  is  to  validate  the dimensions  and  properties  of  a  given  structure.  The  dimensions  like  for instance the thickness of a construction element should  be measured after finishing  building  it.  The  aim  is  to  compare  the  measured  value  with  the design  value   to  avoid   that   elements  do   not  correspond  to  the  input requirements.  Moreover,  the  measurements  are  helpful  to  analyse  the statistical    distribution    of    the    investigated    geometrical    property    by computing e.g. a histogram, which visualises the dispersion and  enable the calculation of the probability of failure for a specific structure or element.In  this  work,  a  shotcrete  layer  has  been  analysed  in  order  to  provide information  about  the  homogeneity  of  the  shotcrete  thickness  in  a  pre-determined  tunnel  section.  The  calculation  method  is  based  on  two  laser scans,  before  and  after  applying  the  shotcrete.  Due  to  the  construction process, the shotcrete layer will not be totally equal, which might be a safety problem. Especially, when  the shotcrete layer is thinner than  required and hence, the actual variation of the shotcrete must be considered and verified.To determine the statistical distribution, correlograms and histograms have been  computed  for  a  wall  area  in  a  tunnel  in  Southern  Sweden.  The correlogram shows the distance where the values have a correlation to each other  and  usually  this  distance  is  called  scale  of  fluctuation.  For  the  wall section, this scale of fluctuation has been calculated for the length (0.8m) as well  as  the  height  (0.8m).  Compared  to  the  original  sample  distance,  e.g. distance of the rock bolts, the variance for the calculation of the probability of failure might be reduced.

An experimental study of active control of fully separated flow over a symmetrical circular-arc airfoil at high angles of attack was performed. The experiments were carried out in a low-speed, open circuit wind tunnel. Angles of attack from 10 to 40 degrees were tested. Low-power input, unsteady excitation was applied to the leading or trailing edge shear layers. The actuation was provided by the periodic oscillation of a 4-percent-chord flap placed on the suction side of the airfoil and facing the sharp edge. Vortex-shedding frequencies were measured and harmonic combinations selected as the applied actuator frequencies. Pressure measurements over the airfoil show that the control increased the normal force coefficient by up to 70%. This supports the idea of vortex capture in the time-averaged sense, enhancing the lift on the airfoil by managing the shear layer roll up. The results indicate the viability of the control of large-scale flow fields by exploiting the natural amplification of disturbances triggered by small-scale actuators. The application of flow control on sharp-edged aircraft wings could lead to improved maneuverability, innovative flight control and weight reduction. These can be achieved by inexpensive, low-power, rugged actuators. / Master of Science

Carpal tunnel syndrome (CTS) is a peripheral median neuropathy that is commonly characterized by thickening and fibrosis of the subsynovial connective tissue (SSCT) surrounding finger flexor tendons. The degenerative process affecting SSCT can be initiated with excessive relative motion between the tendon and SSCT that ruptures interconnecting collagen. We used colour Doppler ultrasound to evaluate flexor digitorum superficialis tendon motion at two movement speeds with palmar compression, forearm compression, and partial ischemia (via brachial blood pressure cuff). Partial ischemia decreased SSCT displacement (22.9 ± 3.3 mm vs. 22.0 ± 3.3 mm; p = 0.015) while tendon displacement did not change. There was also a trend for increased relative tendon-SSCT displacement and shear strain index (SSI – relative displacement normalized to tendon displacement), which suggested partial ischemia might increase the strain in collagen that connects tendon and SSCT. Forearm compression decreased tendon displacement (28.5 ± 4.1 mm vs. 27.0 ± 4.6 mm; p = 0.043) while SSCT displacement also trended to decrease (24.0 ± mm vs. 22.5 mm; p = 0.059). With a lack of change in relative tendon-SSCT displacement and SSI, maintaining flexion-extension range of motion may have meant that forearm compression strained the musculotendinous unit at a location where SSCT was uncompromised. Palmar compression did not significantly affect any dependent motion variables, which suggested palmar compressive forces likely do not affect tendon-SSCT shear injury risk. The fast movement speed increased relative tendon-SSCT displacement and SSI while decreasing mean velocity ratio (MVR), which suggested greater tendon-SSCT shear strain in all baseline and compression conditions. Previously, increased relative tendon-SSCT displacement with fast movement speed was only shown in cadaveric investigations, but we confirmed this effect is transferable in an in vivo model. We induced ischemia proximally and found a reduction in SSCT displacement at the distal carpal tunnel. This finding suggests that the vascular network integrated within SSCT may play a role in altering tendon-SSCT excursion, independent of other external mechanical factors previously shown to increase relative motion and potential shear injury risk. Overall, this thesis showed that external mechanical compression at the palm or forearm likely do not negatively affect relative tendon-SSCT motion and that local ischemia and carpal tunnel blood flow should be considered when evaluating tendon and SSCT motion in relation to CTS development and progression. / Thesis / Master of Science (MSc)

This thesis deals with the problems of scaling aerodynamic data from wind tunnel conditions to free flight. The main challenges when this scaling should be performed is how the model support, wall interference and the potentially lower Reynolds number in the wind tunnel should be corrected. Computational Fluid Dynamics (CFD) simulations have been performed on a modern transonic transport aircraft in order to reveal Reynolds number effects and how these should be scaled accurately. This investigation also examined how the European Transonic Wind tunnel (ETW) twin sting model support influences the flow over the aircraft. In order to further examine Reynolds number effects a MATLAB based code capable of extracting local boundary layer properties from structured and unstructured CFD calculations have been developed and validated against wind tunnel measurements. A general scaling methodology is presented. / QC 20101123

The Turbulent Heat Transfer Test Facility (THTTF) has been refurbished and the data acquisition system upgraded. The THTTF is now controlled by a LabView 4.1 program which replaces the old program in BASIC. Heat transfer data acquired using this new program is presented as Stanton number distributions. The new data set is compared to previously reported data obtained with this facility and other wellepted published data. This project has successfully qualified the THTTF for zero-pressure gradient, isothermal wall temperature, incompressible boundary-layer flow over smooth flat plates without transpiration. The THTTF is now set to accommodate modifications which will facilitate heat transfer investigations with high freestream turbulence.