Validation study of large-eddy simulations of wake stabilized reacting flows using artificial flame thickening approaches

Wake flows are the preferred mode of flame stabilization in lean premixed combustion in gas turbine engines, low NOx burners, afterburners etc. These flows exhibit inherent unsteadiness and for their numerical modeling and simulations, large eddy simulation (LES) techniques with an appropriate combustion model and reaction mechanism afford a balance between computational complexity and predictive accuracy. Before using them in practical systems, these techniques must be validated against experimental measurements in a number of canonical cases. In this work, results from LES of non-reacting and reacting flows are compared to data from a number of experiments, corresponding to the following configurations: a triangular bluff body in a rectangular duct, a backward facing step, and a cylindrical sudden expansion with swirl. The artificial flame thickening approach is applied for modeling turbulence-combustion interactions at small scales. Algebraic and equationbased efficiency function models are implemented, along with an appropriate reduced chemistry mechanism. A novel dynamic formulation for the efficiency function based on the flame-wrinkling equation that explicitly incorporates the influence of strain and time-history effects is proposed, and a detailed combustion chemistry mechanism is also used. Results show that the approaches are effective in simulating turbulent premixed combustion

Multi-agent motion planning for nonlinear Gaussian systems

In this paper, a multi-agent motion planner is developed for nonlinear Gaussian systems using a combination of probabilistic approaches and a rapidly exploring random tree (RRT) algorithm. A closed-loop model consisting of a controller and estimation loops is used to predict future distributions to manage the level of uncertainty in the path planner. The closed-loop model assumes the existence of a feedback control law that drives the actual system towards a nominal system. This ensures the uncertainty in the evolution does not grow significantly and the tracking errors are bounded. To trade conservatism with the risk of infeasibility and failure, we use probabilistic constraints to limit the probability of constraint violation. The probability of leaving the configuration space is included by using a chance constraint approach and the probability of closeness between two agents is imposed using an overlapping coefficient approach. We augment these approaches with the RRT algorithm to develop a robust path planner. Conflict among agents is resolved using a priority-based technique. Numerical results are presented to demonstrate the effectiveness of the planner

Methodology for Path Planning with Dynamic Data-Driven Flight Capability Estimation

This paper presents methodology to enable path planning for an unmanned aerial vehicle that uses dynamic data-driven flight capability estimation. The main contribution of the work is a general mathematical approach that leverages offline vehicle analysis and design data together with onboard sensor measurements to achieve dynamic path planning. The mathematical framework, expressed as a Constrained Partially Observable Markov Decision Process, accounts for vehicle capability constraints and is robust to modeling error and disturbances in both the vehicle process and measurement models. Vehicle capability constraints are incorporated using Probabilistic Support Vector Machine surrogates of high-fidelity physics-based models that adequately capture the richness of the vehicle dynamics. Sensor measurements are treated in a general manner and can include combinations of multiple modalities such as GPS/IMU data as well as structural strain data of the airframe. Results are presented for a simulated 3-D environment and point-mass airplane model. The vehicle can dynamically adjust its trajectory according to the observations it receives about its current state of health, thereby retaining a high probability of survival and mission success

The management of complicated colorectal cancer in older patients in a global perspective after COVID-19: the CO-OLDER WSES project

BACKGROUND: Colorectal (CRC) cancer is becoming a disease of the elderly. Ageing is the most significant risk factor for presenting CRC. Early diagnosis of CRC and management is the best way in achieving good outcomes and longer survival but patients aged ≥75 years are usually not screened for CRC. This group of patients is often required to be managed when they are symptomatic in the emergency setting with high morbidity and mortality rates. Our main aim is to provide clinical data about the management of elderly patients presenting complicated colorectal cancer who required emergency surgical management to improve their care. METHODS: The management of complicated COlorectal cancer in OLDER patients (CO-OLDER; ClinicalTrials.gov ID: NCT05788224; evaluated by the local ethical committee CPP EST III-France with the national number 2023-A01094-41) in the emergency setting project provides carrying out an observational multicenter international cohort study aimed to collect data about patients aged ≥75 years to assess modifiable risk factors for negative outcomes and mortality correlated to the emergency surgical management of this group of patients at risk admitted with a complicated (obstructed and perforated) CRC. The CO-OLDER protocol was approved by Institutional Review Board and released. Each CO-OLDER collaborator is asked to enroll ≥25 patients over a study period from 1st January 2018 to 30th October 2023. Data will be analyzed comparing two periods of study: before and after the COVID-19 pandemic. A sample size of 240 prospectively enrolled patients with obstructed colorectal cancer in a 5-month period was calculated. The secured database for entering anonymized data will be available for the period necessary to achieve the highest possible participation. RESULTS: One hundred eighty hospitals asked to be a CO-OLDER collaborator, with 36 potentially involved countries over the world. CONCLUSIONS: The CO-OLDER project aims to improve the management of elderly people presenting with a complicated colorectal cancer in the emergency setting. Our observational global study can provide valuable data on the effectiveness of different management strategies in improving primary assessment, management and outcomes for elderly patients with obstructed or perforated colorectal cancer in the emergency setting, guiding clinical decision-making. This information can help healthcare providers make informed decisions about the best course of action for these patients