Dynamic models to reconstruct ancient landscapes

In this paper a method of landscape analysis is demonstrated through raster-based digital elevation models (DEM) using the case-study of the Helike Delta, Gulf of Corinth, Greece. In the Classical Period, Helike was the seat of the Achaean League and the worship centre of the god Helikonian Poseidon. With the focus on the earthquake and tsunami of 373BC, DEMs are generated using dynamic models of sea level rise, tectonic and pulse tectonic uplift, sub-sidence, and sediment deposition. Starting with a DEM from the present day landscape, simulated DEM models are generated for the Early Helladic II/III (2500-2100BC), Classical (480-323BC), Hellenistic (323-146 BC), and Roman (1st Century BC – 4th Century AD Periods). The models shed light on archaeological interpretation concerning the continuity and discontinuity of human occupation in the Helike Delta. Moreover, the method demonstrates a new approach to dynamic landscape analysis using GIS that is general and can be applied to any landscape. Keywords: GIS, dynamic models, raster-based DEM, landscape analysis, geomorphology, geoarchaeology, Helike Delt

A Summary of Computations of Ingestion at the University of Bath

Rim seals in gas turbines are used to reduce the potentiallydamaging ingestion of hot gas into the rotor-stator wheel-space of aturbine stage. Sealing air, bled from the compressor, is also used toreduce or prevent ingestion, but this can be at the expense of stageefficiency.This paper summarises recent research into the computation ofthe fluid dynamics and heat transfer of ingestion carried out at theUniversity of Bath. 3D Unsteady Reynolds-averaged Navier-Stokes (URANS) simulations have been carried out, and muchmore economical simplified steady state computational modelshave also been tested. The results of the computations are comparedwith experimental measurements (also made at the University) ofpressure, tracer gas concentration based sealing effectiveness, swirland heat transfer for different generic and also engine-representative rim seals. The computations allow insight intothe flow physics of ingestion and factors affecting the most efficientuse of sealing air, as well as providing information to support thedevelopment of the theoretical models of ingestion that are usefulto engine designers. The experimental test facility permits measurementand ranking of sealing effectiveness for a range of differentrim seal configurations

Whither Digital Archaeological Knowledge? The Challenge of Unstable Futures

Digital technology increasingly pervades all settings of archaeological practice and virtually every stage of knowledge production. Through the digital we create, develop, manage and share our disciplinary crown jewels. However, technology adoption and digital mediation has not been uniform across all settings or stages. This diversity might be celebrated as reflecting greater openness and multivocality in the discipline, but equally it can be argued that such diversity is unsustainable, and that standards are insufficiently rigorous. Regardless, all positions face the possibility of being severely tested by some large-scale external event: on every continent we witness economic and political upheaval, violence and social conflict. How is digitally mediated knowledge created, managed, and disseminated by archaeologists today, and how secure are the means by which this is achieved? To investigate this question we apply the futurity technique of scenario analysis to generate plausible scenarios and assess their strategic strengths and weaknesses. Based on this analysis we propose some measures to place archaeology in a more robust knowledgescape without stifling digitally creative disruption

Model of Effect of Hot Gas Ingress on Temperatures of Turbine Disks

Ingress is the leakage of hot mainstream gas through the rim-seal clearance into the wheel-space between the rotating turbine disk (the rotor) and the adjacent stationary casing (the stator). The high-pressure rotor is purged by a radial outflow of air from the high-pressure compressor, and this cooling air is also used to reduce the ingress. The engine designer needs to predict the stator and rotor temperatures as a function of cooling-flow rate. The sealing effectiveness determines how much air is needed to reduce or prevent ingress; although there are numerous theoretical and experimental papers on the effectiveness of different seal geometries, there are few papers on the effect of ingress on the temperature of the rotating disk. This is an unsolved problem of great practical importance: under high stress, a small increase in metal temperature can significantly reduce operating life. In this paper, conservation equations and control volumes are used to develop theoretical equations for the exchange of mass, concentration and enthalpy in an adiabatic rotor-stator system when ingress occurs. It is assumed that there are boundary layers on the rotor and stator, separated by an inviscid rotating core, and the fluid entrained from the core into the boundary layer on the rotor is recirculated into that on the stator. The superposed cooling flow protects the rotor surface from the adverse effects of hot-gas ingress, which increases the temperature of the fluid entrained into the rotor boundary layer. A theoretical model has been developed to predict the relationship between the sealing effectiveness on the stator and the adiabatic effectiveness on the rotor, including the effects of both ingress and frictional heating. The model involves the use of a nondimensional buffer parameter, Ψ, which is related to the relative amount of fluid entrained into the rotor boundary layer. The analysis shows that the cooling flow acts as a buffer, which attenuates the effect of hot gas ingress on the rotor, but frictional heating reduces the buffer effect. The theoretical effectiveness curves are in good agreement with experimental data obtained from a rotor-stator heat-transfer rig, and the results confirm that the buffer effect increases as the sealing effectiveness of the rim seals decreases. The analysis quantifies the increase in the adiabatic rotor temperature due to direct frictional heating, which is separate from the increase due to the combined effects of the ingress and the indirect frictional heating of the entrained fluid. These combined effects are reduced as Ψ increases, and Ψ = 1 at a critical flow rate above which there is no entrained fluid and consequently no indirect heating of the rotor. The model also challenges the conventional physical interpretation of ingress as, in general, not all the hot gas that enters the rim-seal clearance can penetrate into the wheel-space. The ingress manifests itself through a mixing of enthalpy, which can be exchanged even if no ingested fluid enters the wheel-space.</p