Dedication

This work is dedicated to my family: my parents, my sister and my grandmother iii Acknowledgments I would like to thank my advisor Dr. Zafer Boybeyi, who provided me the opportunity to embark upon this journey. Without his continuous moral and scientific support at every level, this work would not have been possible. Taking on the rather risky move of giving me 100 % freedom in research from the beginning certainly deserves my greatest acknowl-edgments. I am also thoroughly indebted to Dr. Pasquale Franzese for his guidance of this research, for the many lengthy – sometimes philosophical – discussions on turbulence and other topics, for being always available and for his painstaking drive with me through the dungeons of research, scientific publishing and aesthetics. My gratitude extends to Dr. Rainald Löhner from whom I had the opportunity to take classes in CFD and to learn how not to get lost in the details. I found his weekly seminars to be one of the best opportunities to learn critical and down-to-earth thinking. I am also indebted to Dr. Nash’at Ahmad for showing me the example that with a careful balance of school, hard work and family nothing is impossible. I thank Dr. Thomas Dreeben for the many helpful and insightful discussions on the velocity model and elliptic relaxation. I am also grateful to the reviewers of our journal papers for their valuable comments and suggestions on our initial manuscripts. I will always remember my professors at home at the Departments of Mathematics