(230ap) Lda Measurement of a Simplified Nasal Cavity

LDA (Laser Doppler anemometry) [1] is a noninvasive flow measurement technique which allows evaluating the velocity components in a flow field. In contrast to other methods the temporal resolution is much higher, so it is possible to get information about the intensity of turbulence to validate time-varying structures in a LB (Lattice Boltzmann) [2] simulation of a simplified nasal cavity. The comparison of LDA and LB should determine whether the numerical calculation fits well with the flow phenomena by nature.In order to get a reliable and successful measurement it is necessary to define the boundaries of the flow. Since breathing process is complex and slightly different at every person, for simplification the maximum flow rate of an adult human from the rhinomanometry [3] (800 ml/s) is taken into account for the measurement. Therefore, a closed loop control system adjusts rotational speed of a fan by the use of a thermal anemometer [4]. Furthermore, the simplified nose model has a bounding box like an ordinary nose, though, the cross section is rectangular. In the middle a flow resistance with the dimensions of 12.5 x 10 mm is positioned. However, the same obstacle can be found within the frontal sinus near the nose entrance. Since the measurement technique uses a sensor to detect interference fringes of two laser lights, reflections would impede the execution heavily. Therefore, the model is made of glass and Plexiglas® elements. The principle of LDA needs moving particles which are in this case generated by an air humidifier. As the LDA setup has two moveable axes the domain will be analyzed in planes. Since the main flow is two dimensional the third velocity direction is neglected due to the simpler setup. Nevertheless, there is the need to do the measurement twice, since only one velocity component can be ascertained. Subsequently, the velocity magnitude is calculated for further investigations and post processing. In order to get out of the measurement points a continuous interpolated velocity function the Delaunay algorithm [5] is applied.This preparatory work helps to find boundary conditions and other numerical parameters for the LB simulation. [1] Boutier, A., Laser velocimetry in fluid mechanics, 2012, ISBN: 978-1-84821-397-5.

[2] Mohamad, A., Lattice Boltzmann Method, Fundamentals and Engineering Applications with computer codes, 2011.

[3] Anniko M., Bernal-Sprekelsen M.,Bonkowsky V.,Bradley P., Iurato S., Otorhinolaryngology, Head and Neck Surgery, Springer Science & Business Media, 2010, ISBN: 978-3-54068-940-9.

[4] Goldstein R., Fluid Mechanics Measurements, Second Edition, 1996, ISBN: 978-1-56032-306-8.

[5] Edelsbrunner, H., Geometry and Topology for Mesh Generation. Cambridge University Press, Cabridge, 2001.