An adjoint-based approach for the surgical correction of nasal septal deviations.

Deviations of the septal wall are widespread anatomic anomalies of the human nose; they vary significantly in shape and location, and often cause the obstruction of the nasal airways. When severe, septal deviations need to be surgically corrected by ear-nose-throat (ENT) specialists. Septoplasty, however, has a low success rate, owing to the lack of suitable standardized clinical tools for assessing type and severity of obstructions, and for surgery planning.

On the comparison between pre- and post-surgery nasal anatomies via computational fluid dynamics.

Nasal breathing difficulties (NBD) are widespread and difficult to diagnose; the failure rate of their surgical corrections is high. Computational fluid dynamics (CFD) enables diagnosis of NBD and surgery planning, by comparing a pre-operative (pre-op) situation with the outcome of virtual surgery (post-op). An equivalent comparison is involved when considering distinct anatomies in the search for the functionally normal nose.

Saving energy in turbulent flows with unsteady pumping.

Viscous dissipation causes significant energy losses in fluid flows; in ducts, laminar flows provide the minimum resistance to the motion, whereas turbulence substantially increases the friction at the wall and the consequent energy requirements for pumping. Great effort is currently being devoted to find new strategies to reduce the energy losses induced by turbulence. Here we propose a simple and novel drag-reduction technique which achieves substantial energy savings in internal flows.

Through The Back Door: Expiratory Accumulation of SARS-Cov-2 in the Olfactory Mucosa as Mechanism for CNS Penetration.

SARS-CoV-2 is a respiratory virus supposed to enter the organism through aerosol or fomite transmission to the nose, eyes and oropharynx. It is responsible for various clinical symptoms, including hyposmia and other neurological ones. Current literature suggests the olfactory mucosa as a port of entry to the CNS, but how the virus reaches the olfactory groove is still unknown.

On the Turbulence Modeling of Blood Flow in a Stenotic Vessel.

Blood flow dynamics in a stenosed, subject-specific carotid bifurcation is numerically simulated using direct numerical simulation (DNS) and Reynolds-averaged Navier-Stokes (RANS) equations closed with turbulence models. DNS is meant to provide a term of comparison for the RANS calculations, which include classic two-equations models (k-ε and k-ω) as well as a transitional three-equations eddy-viscosity model (kT-kL-ω). Pulsatile inlet conditions based on in vivo ultrasound measurements of blood velocity are used.

Large eddy simulations of blood dynamics in abdominal aortic aneurysms.

We study the effects of transition to turbulence in abdominal aortic aneurysms (AAA). The presence of transitional effects in such districts is related to the heart pulsatility and the sudden change of diameter of the vessels, and has been recorded by means of clinical measures as well as of computational studies. Here we propose, for the first time, the use of a large eddy simulation (LES) model to accurately describe transition to turbulence in realistic scenarios of AAA obtained from radiological images.

Effects of CT resolution and radiodensity threshold on the CFD evaluation of nasal airflow.

The article focuses on the robustness of a CFD-based procedure for the quantitative evaluation of the nasal airflow. CFD ability to yield robust results with respect to the unavoidable procedural and modeling inaccuracies must be demonstrated to allow this tool to become part of the clinical practice in this field. The present article specifically addresses the sensitivity of the CFD procedure to the spatial resolution of the available CT scans, as well as to the choice of the segmentation level of the CT images.

Review of computational fluid dynamics in the assessment of nasal air flow and analysis of its limitations.

Nasal breathing difficulties (NBD) are a widespread medical condition, yet decisions pertaining to the surgical treatment of chronic NBD still imply a significant degree of subjective judgement of the surgeon. The current standard objective examinations for nasal flow, e.g.

Drag reduction in turbulent boundary layers by in-plane wall motion.

Drag-reduction techniques capable of reducing the level of turbulent friction through wall-parallel movement of the wall are described, with special emphasis placed on spanwise movement. The discussion is confined to active open-loop control strategies, although feedback control is briefly mentioned with regard to peculiarities of spanwise sensing and/or actuation. Theoretical considerations are first given to explain why spanwise motion is expected to be particularly effective in skin-friction drag reduction.

Direct-numerical-simulation-based measurement of the mean impulse response of homogeneous isotropic turbulence.

A technique for measuring the mean impulse response function of stationary homogeneous isotropic turbulence is proposed. Such a measurement is carried out here on the basis of direct numerical simulation (DNS). A zero-mean white-noise volume forcing is used to probe the turbulent flow, and the response function is obtained by accumulating the space-time correlation between the white forcing and the velocity field.