Low cost on-line non-invasive sewer flow monitoring

A novel acoustic sensor has been developed, capable of remotely monitoring the free surface 'fingerprint' of shallow flows. Temporal and spatial properties of this pattern are shown to contain information regarding the nature of the flow itself. The remote measurement can thereby be used to infer the bulk flow properties such as depth, velocity, and the hydraulic roughness of the pipe. The instrument is non-invasive and is also low cost, low maintenance, and low power. Such a device will allow for widespread monitoring of flow conditions in drainage networks, enabling pro-active maintenance and reliable real-time control. © IWA Publishing 2013

Rapid detection of sewer defects and blockages using acoustic-based instrumentation

Sewer flooding incidents in the UK are being increasingly associated with the presence of blockages. Blockages are difficult to deal with as although there are locations where they are more likely to occur, they do occur intermittently. In order to manage sewer blockage pro-actively sewer managers need to be able to identify the location of blockages promptly. Traditional closed-circuit television (CCTV) inspection technologies are slow and relatively expensive so are not well suited to the rapid inspection of a network. This is needed if managers are to be able to address sewer blockages pro-actively. This paper reports on the development of an acoustic-based sensor. The sensor was tested in a full scale sewer pipe in the laboratory and it was shown that it is able to find blockages and identify structural aspects of a sewer pipe such as a manhole and lateral connection. Analysis of the received signal will locate a blockage and also provide information on its character. The measurement is very rapid and objective and so inspections can be carried out at much faster rates than using existing CCTV technologies

Sewer inspection and comparison of acoustic and CCTV methods

In the UK, the majority of sewer pipe inspections are carried out using closed-circuit television (CCTV) technology. This inspection technology is expensive; given the size of the UK sewer network, this means that only a small sample of network is inspected regularly. Up-to-date condition information on individual sewers is required to minimise sewer network operation failures and, ultimately, to eliminate flooding. There is therefore a need for a quicker and cheaper inspection method. This paper reports on a novel low-cost acoustic sensor system that can be used for the rapid detection of various defects in sewer pipes. It is shown that a large number of pipe defects can be classified and validated against CCTV images by way of visual examination of the acoustical data presented in the form of spectrograms. An overview of the technological principles used by the acoustic inspection method is presented in this paper together with the results of field trial surveys. The new method was tested in operational sewers in Austria and the acoustic inspection results compared with available CCTV reports: 79% of the defects identified by CCTV were also detected using the acoustic technique

Free-surface behaviour of shallow turbulent flows

Over the last two decades, interest in the free surface behaviour of gravity-driven shallow turbulent flows has increased considerably. It is believed that observation of free surface behaviour can provide useful information about the hydrodynamic characteristics of the flow and enable remote retrieval of these characteristics to non-invasively and rapidly monitor river flows. At the current state literature presents scattered knowledge and also exhibits non-uniformity in the terminology used. This paper is a review of the state-of-art of this area of research and was created with two objectives: to gather the information relevant to understand the linkages between the free surface behaviour and underpinning hydrodynamic processes while using a uniform terminology, and to analyse the gaps in our knowledge of this critical topic

Using noncontact measurement of water surface dynamics to estimate river discharge

Estimating river discharge requires simultaneous measurement of velocity and flow depth. While surface velocities are relatively easy to measure using noncontact techniques, depth measurement usually requires physically intrusive instrumentation. This limits our capability to remotely monitor discharge in natural rivers subject to bed level variations. This work tests the potential to estimate the surface velocity, the water depth, the depth average velocity, and then discharge of a river using only a sequence of images of the dynamic water surface. The method is based on a comparison between the spatiotemporal Fourier spectra of the pixel intensities of these images and the theoretical dispersion relations of turbulence-generated surface fluctuations and gravity-capillary waves. The method is validated through the analysis of water surface videos obtained with fixed cameras from two river sections equipped with conventional discharge gauging. The applicability of the approach is demonstrated and the measurement uncertainties are quantified. The method is affected by two main sources of uncertainty: one derives from the estimation of the velocity index and the other from the obtainable resolution of the Fourier analysis. This resolution strongly controls the observation of depth and/or velocity variations in space and in time. The technique has advantages over current approaches: it has clear physical foundations; the equipment is low cost and is highly mobile; it does not need artificial tracers or physical equipment to measure depth; and it can directly provide estimates of the key flow parameters just from time series of images of the water surface

Opaque Branes in Warped Backgrounds

We examine localized kinetic terms for gauge fields which can propagate into compact, warped extra dimensions. We show that these terms can have a relevant impact on the values of the Kaluza-Klein (KK) gauge field masses, wave functions, and couplings to brane and bulk matter. The resulting phenomenological implications are discussed. In particular, we show that the presence of opaque branes, with non-vanishing brane-localized gauge kinetic terms, allow much lower values of the lightest KK mode than in the case of transparent branes. Moreover, we show that if the large discrepancies among the different determinations of the weak mixing angle would be solved in favor of the value obtained from the lepton asymmetries, bulk electroweak gauge fields in warped-extra dimensions may lead to an improvement of the agreement of the fit to the electroweak precision data for a Higgs mass of the order of the weak scale and a mass of the first gauge boson KK excitation most likely within reach of the LHC.Comment: 37 pages, 12 figures, improved analysis of the precision electroweak constraint

Precision Electroweak Data and Unification of Couplings in Warped Extra Dimensions

Warped extra dimensions allow a novel way of solving the hierarchy problem, with all fundamental mass parameters of the theory naturally of the order of the Planck scale. The observable value of the Higgs vacuum expectation value is red-shifted, due to the localization of the Higgs field in the extra dimension. It has been recently observed that, when the gauge fields propagate in the bulk, unification of the gauge couplings may be achieved. Moreover, the propagation of fermions in the bulk allows for a simple solution to potentially dangerous proton decay problems. However, bulk gauge fields and fermions pose a phenomenological challenge, since they tend to induce large corrections to the precision electroweak observables. In this article, we study in detail the effect of gauge and fermion fields propagating in the bulk in the presence of gauge brane kinetic terms compatible with gauge coupling unification, and we present ways of obtaining a consistent description of experimental data, while allowing values of the first Kaluza Klein mode masses of the order of a few TeV.Comment: 32 pages, 7 figures. References adde

Reconstruction of the frequency-wavenumber spectrum of water waves with an airborne acoustic Doppler array for non-contact river monitoring

This work presents a novel method to reconstruct the frequency-wavenumber spectrum of water waves based on the complex acoustic Doppler spectra of scattered sound measured with an array of microphones. The reconstruction is based on a first-order small-roughness-amplitude expansion of the acoustic wave scattering equation, which is discretized and inverted by means of a singular value decomposition. An analogy of this approach to the first-order Bragg scattering problem is demonstrated by means of a stationary phase expansion. The approach enables the reconstruction of the dispersion relation of water waves when the ratio between roughness height and acoustic wavelength is less than 0.1, and when the surface wavelength is larger than 1/2 of the acoustic wavelength. The method is validated against synthetic data and data from laboratory and field experiments, to demonstrate its applicability to two-and three-dimensional complex patterns of water waves, and specifically to the surface deformations that arise naturally in a turbulent open-channel flow. Fitting the reconstructed data with the analytical dispersion relation enables the non-contact estimate of the underlying flow velocity for hydraulic conditions where the coexistence of different types of turbulence-forced and freely propagating water waves would limit the accuracy of standard non-contact Doppler velocimetry approaches, paving the way for robust and accurate non-contact river monitoring using acoustics