Martin Berggren

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In order to laminarize an unsteady, internal flow, the vorticity field is minimized, in a least-squares sense, using an optimal-control approach. The flow model is the Navier–Stokes equation for a viscous incompressible fluid, and the flow is controlled by suction and blowing on a part of the boundary. A quasi-Newton method is used for the minimization of a(More)
Standard weak solutions to the Poisson problem on a bounded domain have squareintegrable derivatives, which limits the admissible regularity of inhomogeneous data. The concept of solution may be further weakened in order to define solutions when data is rough, such as for inhomogeneous Dirichlet data that is only square-integrable over the boundary. Such(More)
C%D ! # ' F # 9 . ) . F + / " %3?G ! H H @ " 0 / H = ) > I J H %3*% ! # ' 9 ) 6 9 0 # @ # (?%& C3D > , # : . , > ) F # # + : + ) # , ' , (4G C(D 6 # 2 : H + , . @ > = 3-$ C*D K : / . . F # 0 / : # , ) F @ $-% C$D / / : , # L ) + 9 / . : # , 6 9 2 ) F @ %(*G C?D . : 9 H L ' M , L @ F L ) F ! 4$-G C4D ! @ 9 ) + > # . @ > : ) @ 0 > # F / 2 6 = . " ! 3%33 ! , 9(More)
Using gradient-based optimization combined with numerical solutions of the Helmholtz equation, we design an acoustic device with high transmission efficiency and even directivity throughout a two-octave-wide frequency range. The device consists of a horn, whose flare is subject to boundary shape optimization, together with an area in front of the horn,(More)
We use a gradient-based material distribution approach to design conductive parts of microstrip antennas in an efficient way. The approach is based on solutions of the 3D Maxwell’s equation computed by the finite-difference time-domain (FDTD) method. Given a set of incoming waves, our objective is to maximize the received energy by determining the(More)
The sensitivity analysis is a crucial step in algorithms for gradient-based aerodynamic shape optimization. The analysis involves computing the gradient of functionals such as drag, lift, or aerodynamic moments, with respect to the parameters of the design. Gradients are efficiently calculated by solving adjoints of the linearized flow equations. The flow(More)