Elif Oguz

The effect of an emergent vegetation (i.e. Phragmistes Australis) on wave attenuation and wave kinematics

ABSTRACT Akgul, M.A., Yilmazer, D., Oguz, E., Kabdasli, M.S., Yagci, O., 2013. The effect of an emergent vegetation (i.e. Phragmistes Australis) on wave attenuation and wave kinematics Coastal vegetation acts as a natural barrier at many coastal zones, protecting the landside against wave effects and coastal erosion. It is known that coastal vegetation affects wave properties, and studies regarding this topic have been made in a wide variety, mostly focusing on wave attenuation. In this study, laboratory experiments have been conducted in a wave basin to inspect the effect of an emergent vegetation on wave attenuation, wave transformation and wave kinematics. A blank area is present along the reed field, which enables energy transformation during wave propagation. Three different regular waves have been sent to a natural reed field, and wave heights and kinematics have been measured around the structure. The results indicate that crest-parallel energy transmission takes place as the waves propagate along the reed field, which is boosted at the end of the reed, and the transmission becomes faster on waves with higher wave steepness. Measured water particle velocities have been evaluated to obtain the steady-cyclic and fluctuation components, by which, turbulence intensities in front and at the wake of the reed field have been evaluated. The results indicate that turbulence intensity increases at the mid-depth at the wake of the structure, becoming higher with increasing wave steepness. Thus, one may conclude that energy dissipation takes further place after the end of the reed field due to turbulence.

The effect of reed beds on wave attenuation and suspended sediment concentration

ABSTRACT Oguz, E., Elginoz, N., Koroglu, A., Kabdasli, M.S., 2013. The effect of reed beds on wave attenuation and suspended sediment concentration. The effect of emergent and submerged vegetation on uniform and oscillatory flow conditions has been intensively studied by researchers in the last two decades. It has been determined that vegetation affects wave characteristics and cause wave attenuation especially in shallow waters where wave orbitals are in interaction with vegetation. Consequently they affect sediment deposition and resuspension acting as a sink. The aim of this study is to determine wave attenuation due to vegetation, and to identify the effect of emergent vegetation on suspended sediment concentration. In this experimental study, a reed bed was established on a sandy bottom in a wave flume in ITU Hydraulics Laboratory. Regular waves with different wave steepness were generated in the flume and water surface elevations through the reed bed were measured using resistance type wave gauges. Suspended sediment concentration time series were measured using OPCON along depth. The gradual wave attenuation due to reed bed was determined and wave transmission coefficients for different waves were found between 0.35 and 0.55 and these values are reversely proportional with wave steepness. It has been found out that wave attenuation also decreases with increasing KC numbers. Suspended sediment concentration measurements inside the reed bed were a little bit harder to interpret, but a decrease in concentration; before the waves reach the reed bed and after the waves left the reed bed, was determined. In spite of many studies on effects of vegetation on flow conditions there is still a lack of understanding vegetation-flow interaction and sedimentation around them. This study is an attempt to make a contribution on this topic.

Failure modes and criticality analysis of the preliminary design phase of the Mars Desert Research Station considering human factors

This work presents an extension to the traditional FMECA (Failure Modes, Effects and Criticality Analysis) method to include the effects of human factors concerning accessibility/repairability, probability of contact and degree of contact. The authors refer to this extension to the traditional FMECA as the Human Design Approach (HDA). All data used in this study was collected during the stay of two of the authors at the Mars Desert Research Station (MDRS) in the Utah desert, USA. The MDRS is a laboratory for carrying out research in order to understand and investigate the difficulties of how to live and work on another planet. The results show that following the HDA can enhance the safety and reliability of the MDRS. There is still a significant amount of research required concerning reliability analysis of the space habitat in terms of the selection of optimum designs, the modification of systems, as well as access, inspection and maintenance strategies, human factors and environmental impacts. This preliminary study will assist the design engineers with the selection of an optimum configuration for space habitats and can be extended to any case where humans can influence function of an environment.