“…Recently, there have been several successful attempts using the adjoint equations in shape optimization (Kuruvila et al, 1994;Anderson and Venkatakrishnan, 1999;Giles and Pierce, 2000;Jameson, 2001;Brezillon and Gauger, 2004;Giering et al, 2005;Carpentieri et al, 2007;Zymaris et al, 2009;Peter and Dwight, 2010;Srinath and Mittal, 2010;Zymaris et al, 2010;Jameson and Ou, 2011), optimal boundary control (Bewley et al, 2001;Collis et al, 2000;Collis et al, 2004) and optimal noise control (Cerviño and Bewley, 2002;Joslin et al, 2005;Wei and Freund, 2006;Spagnoli and Airiau, 2008;Babucke et al, 2009;Kim et al, 2010;Rumpfkeil and Zingg, 2010;Schulze et al, 2011). However, because of the expensive iterative optimization procedure, which involves solving the adjoint equations backward in time and which necessitates the storage of the flow fields obtained during the solution of the Navier-Stokes equations, calculations for the purpose of noise reduction have been carried out almost exclusively for 2D-DNS only and recently for 3D-LES in Kim et al (2010).…”