Prediction of cavitating propeller underwater radiated noise using RANS & DES-based hybrid method

This study focuses on the prediction of the hydrodynamic and hydroacoustic performance of a cavitating marine propeller in open water condition using Reynolds-averaged Navier-Stokes (RANS) and Detached Eddy Simulation (DES) solvers. The effectiveness of the methods is investigated for the recently introduced benchmark propeller that belongs to the research vessel "The Princess Royal". The main emphasis of the study is to examine the capabilities of the RANS and DES solvers for predicting the hydrodynamic performance of a propeller in the presence of sheet and tip vortex cavitation (TVC). In the numerical simulations of the cavitating propeller flow, the Schnerr-Sauer cavitation model based on a reduced Rayleigh-Plesset equation was used to model the sheet and tip vortex cavitation. An alternative vorticity-based adaptive mesh refinement (VAMR) technique was employed for the accurate realisation of the TVC in the propeller's slipstream. In the hydroacoustic calculations, a porous Ffowcs Williams Hawkings equation (P-FWH) was employed together with the DES solver. The numerical hydrodynamic and hydroacoustic results are compared with those of experimental data for the benchmark propeller available from the University of Genova Cavitation Tunnel. The results show that both the RANS and DES solvers are successful for modelling of the sheet cavitation on the propeller blades. However, the prediction of the TVC extension using the RANS solver is found to be insufficient in comparison to the TVC prediction when using the DES method. This is due to the inherent modelling limitations of the RANS solver. In addition to hydrodynamic performance predictions, the overall noise spectrums were found in an agreement with the experimental data with discrepancies between the low and high-frequency region

Numerical investigation of full-scale cavitating propeller underwater radiated noise

This study aims to predict the full-scale propeller Underwater Radiated Noise (URN) in cavitating and non-uniform flow conditions using a viscous flow-based hybrid method. The recently introduced benchmark propeller of the research vessel, "The Princess Royal", was used for the numerical application to validate the methodology presented in this paper. The hybrid method constitutes a DES (Detached Eddy Simulation) solver coupled with a porous formulation of the Ffowcs Williams Hawking Equations (P-FWH) for the URN predictions. The Schnerr-Sauer cavitation model based on the reduced Rayleigh-Plesset equation was utilised to model the sheet and tip vortex cavitation (TVC). A vorticity-based Adaptive Mesh Refinement (V-AMR) technique was proposed and implemented for better modelling of the TVC in the propeller's slipstream. The hydrodynamic performance, including the cavity patterns and URN results, were compared with the full-scale URN data collected from the sea trials with The Princess Royal. The predicted propeller URN results show good agreement with the trials data except for some discrepancies in the high-frequency region of the noise spectra investigated

Dopaminergic and opioidergic regulation during anticipation and consumption of social and nonsocial rewards

The observation of animal orofacial and behavioral reactions has played a fundamental role in research on reward but is seldom assessed in humans. Healthy volunteers (N = 131) received 400 mg of the dopaminergic antagonist amisulpride, 50 mg of the opioidergic antagonist naltrexone, or placebo. Subjective ratings, physical effort, and facial reactions to matched primary social (affective touch) and nonsocial (food) rewards were assessed. Both drugs resulted in lower physical effort and greater negative facial reactions during reward anticipation, especially of food rewards. Only opioidergic manipulation through naltrexone led to a reduction in positive facial reactions to liked rewards during reward consumption. Subjective ratings of wanting and liking were not modulated by either drug. Results suggest that facial reactions during anticipated and experienced pleasure rely on partly different neurochemical systems, and also that the neurochemical bases for food and touch rewards are not identical

Understanding the Use of Academic Research in Science Education Practitioner Journals

This bibliometric study investigated the extent to which science education practitioner journals (SEPJs) cite science education research journals and other resources, and in what proportions. The study found that articles in SEPJs rarely cite the leading science education research journals; the average citation rate per article is well below one. This result was not affected by article type and remains stable across 2013 to 2017. While results indicate the article purpose in the SEPJs affected the proportion of science education research journal citations, the proportion remains low with—in the best case—about 8% of all citations in The Science Teacher from 2013 to 2017. The presentation discusses the role of SEPJ authors of different roles/backgrounds in science education and their use of references. Implications for pedagogical content knowledge (PCK) development and the translation of research to practice are described

The Douglas-Fir Genome Sequence Reveals Specialization of the Photosynthetic Apparatus in Pinaceae.

A reference genome sequence for Pseudotsuga menziesii var. menziesii (Mirb.) Franco (Coastal Douglas-fir) is reported, thus providing a reference sequence for a third genus of the family Pinaceae. The contiguity and quality of the genome assembly far exceeds that of other conifer reference genome sequences (contig N50 = 44,136 bp and scaffold N50 = 340,704 bp). Incremental improvements in sequencing and assembly technologies are in part responsible for the higher quality reference genome, but it may also be due to a slightly lower exact repeat content in Douglas-fir vs. pine and spruce. Comparative genome annotation with angiosperm species reveals gene-family expansion and contraction in Douglas-fir and other conifers which may account for some of the major morphological and physiological differences between the two major plant groups. Notable differences in the size of the NDH-complex gene family and genes underlying the functional basis of shade tolerance/intolerance were observed. This reference genome sequence not only provides an important resource for Douglas-fir breeders and geneticists but also sheds additional light on the evolutionary processes that have led to the divergence of modern angiosperms from the more ancient gymnosperms

Numerical cavitation noise prediction of a benchmark research vessel propeller

This paper presents the preliminary results of a numerical study for noise prediction of a benchmark propeller in open water/uniform flow conditions. The experimental benchmark test data for the research vessel, “The Princess Royal”, were used for validation purposes. The numerical analyses were implemented by using a viscous solver based on the finite volume method while the experimental data were obtained from model tests conducted at the Genova University Cavitation Tunnel. The main aim of the study is to predict propeller hydro-acoustic performance under cavitating conditions. The hydrodynamic flow field was solved using a RANS (Reynolds-averaged Navier-Stokes) solver. The Schnerr-Sauer cavitation model based on a reduced Rayleigh-Plesset equation together with a VOF approach was used to model sheet cavitation on the propeller blades. The computed hydrodynamic characteristics and sheet cavity patterns were shown to be in good agreement with the Genoa experimental data, thus providing a firm basis for cavitating noise predictions. The hydro-acoustic performance of the model propeller was predicted by using a hybrid method. In the noise simulations, RANS equations were equipped with a porous FW-H (Ffowcs Williams-Hawkings) formulation. The different propeller operational conditions were simulated using this hybrid method. The numerical results were also validated with the experimental data for the propeller hydro-acoustic performance. Whereas such validations showed promising results by means of overall noise spectrum with the benchmark test cases in the low-frequency range, the numerical prediction overestimated the 1st BPF values (around 20 dB) in five loading conditions. Besides, in some loading conditions, especially between 200 and 800 Hz, the difference between numerical predictions and the experiment was found around 5–10 dB

Underwater noise measurements with a ship retrofitted with PressurePoresTM noise mitigation technology and using HyDroneTM system

This paper presents the sea trials results by measuring the underwater radiated noise (URN) levels of a research vessel retrofitted with the novel "PressurePoresTM" URN mitigation technology on her propellers to demonstrate the effectiveness of this technology in full-scale. Tip Vortex Cavitation (TVC) is one of the main contributors to a URN. So the strategic implementation of the PressurePoresTM is aimed to reduce the TVC and subsequent URN of ship propellers. During the sea-trials, the URN levels were measured when the vessel's propellers were in the unmodified (without PressurePores) and modified (with PressurePores) conditions, including comprehensive cavitation observations using a high-speed camera to assess PressurePoresTM technology. The trial results showed this innovative technology could mitigate the TVC and resulting URN signature by 10dB. Also, in this measurement campaign, a novel URN measurement method using an aerial drone with a miniature hydrophone called the "HyDroneTM" system was tried successfully. HyDroneTM can be a flexible and practical alternative URN measurement technique to the conventional tethered-based method to improve the undesirable background noise corrections

On the relationship of first-episode psychosis to the amphetamine-sensitized state: a dopamine D2/3 receptor agonist radioligand study.

Schizophrenia is characterized by increased behavioral and neurochemical responses to dopamine-releasing drugs. This prompted the hypothesis of psychosis as a state of "endogenous" sensitization of the dopamine system although the exact basis of dopaminergic disturbances and the possible role of prefrontal cortical regulation have remained uncertain. To show that patients with first-episode psychosis release more dopamine upon amphetamine-stimulation than healthy volunteers, and to reveal for the first time that prospective sensitization induced by repeated amphetamine exposure increases dopamine-release in stimulant-naïve healthy volunteers to levels observed in patients, we collected data on amphetamine-induced dopamine release using the dopamine D2/3 receptor agonist radioligand [11C]-(+)-PHNO and positron emission tomography. Healthy volunteers (n = 28, 14 female) underwent a baseline and then a post-amphetamine scan before and after a mildly sensitizing regimen of repeated oral amphetamine. Unmedicated patients with first-episode psychosis (n = 21; 6 female) underwent a single pair of baseline and then post-amphetamine scans. Furthermore, T1 weighted magnetic resonance imaging of the prefrontal cortex was performed. Patients with first-episode psychosis showed larger release of dopamine compared to healthy volunteers. After sensitization of healthy volunteers their dopamine release was significantly amplified and no longer different from that seen in patients. Healthy volunteers showed a negative correlation between prefrontal cortical volume and dopamine release. There was no such relationship after sensitization or in patients. Our data in patients with untreated first-episode psychosis confirm the "endogenous sensitization" hypothesis and support the notion of impaired prefrontal control of the dopamine system in schizophrenia

Localization Techniques for Non-Palpable Breast Lesions : Current Status, Knowledge Gaps, and Rationale for the MELODY Study (EUBREAST-4/iBRA-NET, NCT 05559411)

Funding: The MELODY study will be financially supported by: Hologic, Merit Medical, Endomag and Sirius Medical.Peer reviewedPublisher PD