Acoustic Flow Measurements and their Applications

The precise measurement of flow rates and water consumption is becoming increasingly important in a globalised world facing major challenges to meet the sustainable usage of natural resources. In addition, process automation and trends such as «Industry 4.0» and the «Internet of Things» have also increased the demands on data quality and granularity in the fields of hydropower, hydrology, waste water, supply and industry.

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Process control via cleaning and disposal.

Drinking water is not the only area requiring flow measurement. The disposal and cleaning of waste water is of equal importance.

Waste water contains a multitude of organic substances which used to be dumped directly into the soil or the nearest river. As awareness has increased, most discharges are now treated to assure long term sustainability. The contamination of surface waters has now been reduced and the oxygen content could be increased once again. Due to the advance of waste water treatment around the world nature was able to regenerate in many places. Today’s civilization is unthinkable without functioning water treatment plants. Modern plants are highly complex systems. They consist of channels for waste water flow, facilities for waste water collection and clarification plants. GWF Technologies GmbH can complete flow measurements in all of these areas.

Further details can be seen in the products.


Operational reasons for flow measurement in sewage treatment plants.

For sewage-treatment plants flow measurements are primarily installed for internal reasons, for example to control specific plant components with flow dependency or for controlling additives. International regulations, for example the EU-Directive for handling municipal waste water, require a continuous surveillance of waste water flow. Defective flow measurements on sewage-treatment plants can therefore influence their operation, but there can also be legal or environmental consequences.


Stationary Pulse-Doppler system – Typical application

Type: Insertion Type

Only for stationary Q-EYE PSC MT with partially filled pipe or with a full filled pipe

Portable Pulse-Doppler system

Type: Mouse

For stationary and portable Q-EYE PSC PRO portable with partially filled pipe or with open channel


Pulse-Wave FFT Technology

Q-Eye Radar MT is an extremely versatile flow measurement system designed for continuous operation and suitable for measurements of flows not only in rivers and open channels, but also in municipal wastewater and storm water sewers. Compact construction combined with the contact-free measurement principle enables an easy installation and use. The maximum permissible installation height above the surface is 30 m. For waste water applications we

The optional ultrasonic depth sensor operates by energizing a piezoelectric transducer with an electronic pulse. This pulse creates a pressure wave that travels to the flow surface where a portion returns to the transducer. Our transmitter offers the best in liquid measurement. It is easy to install, eliminates maintenance caused by sensor fouling and your personnel do not get in contact with the fluid during installation.

Advantages of non-contact measurement

Advantages of non-contact measurement

In some applications it is an advantage to have a non-contact measurement. By combining both radar and water level transmitter, they provide a revolutionary approach to open channel and sewer flow monitoring. Combined are pulse wave radar velocity sensing technology with ultrasonic pulse echo level sensing to measure open channel flows.


Long series of measurements as data basis

Numerous rivers intersect our landscape from small brooks up to huge river networks. Some of them form a natural border between two countries. At all times man has preferred to live in river areas. Clear water, the possibility to use the river for transport, generating power from water and the scenic beauty are amongst the reasons. However, our actions have more and more influence on water quantity and quality. In many regions taking water for irrigation or as drinking water are the reasons. More than half of all big rivers around the world have been polluted during the course of time. Observations of water levels have been used since ancient times, systematic flow measurements go back to the middle of the 19th century. This historical data has been used as the basis for various applications, for example for flood protection and flood forecasting. They also form the foundation for the design of hydroengineering constructions.

In recent years the acoustic flow measurement has established itself as the standard method for measurements on many hydrological stations. With this almost contact free technology
data can be recorded continuously and it provides 24/7 monitoring.

Further details can be seen in the products.


Travel time system with digital signal processing.

The range of application for Fluvius TT runs from small waterways to huge river systems with high suspended solids. By means of acoustic transmission a coded signal is sent through the water and the transit time is calculated providing the speed of river flow. When an acoustic wave propagates in water, part of the energy is damped by friction and suspended solids. This procedure is frequency-related. The higher the frequency, the bigger the damping. For wider distances we use low frequencies as they allow for a considerably better receiver signal.


Transducers depending on width or sediment loads.

The use of the transducer is directly dependent on the use in the appropriate medium. Depending on the acoustic length (typical channel width) and suspended matter content (in g / m3), the corresponding model must be used.

Further details can be seen in the products.


Main task to detect water loss early.

Channels are artificially created waterways used for shipping, transportation, irrigation, drainage and for cooling water extraction of power plants.

A further important use is the transportation of water used for the supply of drinking water. Here the focus lies on detecting water loss at an early stage; sometimes it is difficult to detect small leakages.Our instruments measure precisely and reliably in order to prevent long term water losses.


Further details can be seen in the products.


Measurement at almost constant water level.

In its most basic form, the system operates with a single pair of transducers. However, it relies upon a relatively stable velocity profile, essentially unaffected by changes in the relation between water level and flow. The main flow has to be parallel to the bank. The relationship between measured velocity and flow is established by hydrometric calibration.


Measurement with cross flows.

In rivers there is a high risk of cross flow. Its intensity depends mainly on the river’s geometry and if there is an upstream bend in the river. Although the cross flow does not influence the quantity of the flow, it may affect the measurement, a second pair of transducers will be necessary. By crosswise arrangement of four transducers, effects of changing flow direction can be eliminated.


Measurement with strong fluctuation of the water level.

An even more accurate flow measurement can be obtained with systems using several planes. The measured result can be further improved by using a multi path system layering each of the acoustic paths in parallel planes one above the other. This negates having an expensive hydrometric calibration. This type of system is suitable for applications with large water level fluctuations, reverse flow or a vertical velocity distribution outside the theoretical normal.


Make optimum use of the fuel water.

Hydro power is an important source of energy which contributes to supplying power to the earth’s population. Today, hydro power plants deliver approximately 3,5 per cent of electric energy generated worldwide. Their share in power generation from renewable resources comes to 18 per cent. In the future this share will continue to grow, as resources of fossil fuels are depleted.

The hydro electric performance depends essentially on the usable altitude difference between upper reservoir and lower reservoir, and hence the flow. In order to use the «fuel» water in an optimal way, this flow has to be monitored without any interruptions.

Further details can be seen in the products.


Travel time system with digital signal processing.

For pipes with a diameter of more than half a meter, acoustic flow measurement systems have long established themselves as a reliable and convenient measurement method. Measurements in several planes are a recommended method to determine the efficiency of the turbine without the need for calibration meeting the latest international standards. Fixed installed equipment form the basis for verifying the efficiency. A deterioration of efficiency can be detected right away and therefore corrections can be initiated at an early stage.


A variety of transducers is available – depending on the requirement

Internal mount assemblies which can be fixed directly to the wall. The transducers are aligned by rotating them in their mounting into a predefined position and then fixed in place by tightening. Feedtrough assemblies for installation through exposed penstock walls with access to the interior and exterior of the penstock flow meter section.

Example: 4 planes crossed according to IEC 41 / ASME PTC 18


The advantages of the clamp-on systems.

A flow meter using clamp-on transducers makes measuring flow non-intrusive and easy from the outside of the pipe. The transducers are installed with little technical effort and without process interruption on the pipeline. Rotationally symmetric flow profiles can be determined with a single acoustic path; nonsymmetric profiles require the use of several acoustic paths.

Example: Clamp-On with 2 acoustic paths


Keep an eye on pipelines.

Although there is enough water on earth and it is not consumed but merely used, drinking water starts to get short. The uneven distribution of water amongst the regions, the rising population and our carelessness leads to a shortage of fresh drinking water. In the future more and more pipelines for drinking water will be built all over the globe. In order to operate huge and complex pipe networks efficiently, flow measurement will be necessary.

Further details can be seen in the products.


The measuring system «ReVision»

The ReVision flow meter is a fully integrated metering solution with up to 10 acoustic paths for liquid fluids. It is a new entry in the GWF Technologies GmbH family of high accuracy acoustic metering products. It increases your profitability with exceptional repeatability and linearity throughout the flow range. Due to the patented velocity profile compensation no flow straightener is needed and no on-site calibration is required.


Installation conditions parameterized in advance.

Space constraints and/or appropriate application configurations lead to complex industrial pipe flows which contain elbows, tees and/or other disturbing and non-uniform elements. This leads to difficulties in installing flow meters at a recommended «optimum» location, which is defined by a minimum distance upstream or downstream of known disturbances like an elbow or pump where a fully developed velocity profile is present. Even with multiple flow sensors, there may still be a significant error which is known as the profile factor.

Prior knowledge of the profile factor can be used to correct the velocity measurements made by flow sensors to a true spatially averaged velocity. The ReVision acoustic system provides detailed information on the flow velocity profile and an accurate measurement of the flow rate can be achieved by rebuilding the whole flow velocity profile across the pipe using predetermined conduit configuration parameters and correction factors. Flow meters are also sensitive to velocity profiles where there is a large rotational component (swirl). Flow meters are also sensitive to velocity profiles where there is a large rotational component (swirl).

Swirl is normally generated by two or more out of plane changes in flow direction (e.g. one elbow/tee that goes from vertical to horizontal followed by an elbow/tee that changes the direction of flow in the horizontal plane). Swirl is present to some extent in almost every application and can generate significant transverse velocity components plus it takes a long distance to dissipate. If the swirl is not centred, it can cause significant errors. Thanks to the predetermined conduit configuration parameters and correction factors, the flow meter measurement accuracy is kept when asymmetric profiles and swirls are present in the pipe.

Example: flow meter after a 90° elbow


«ReVision» combined with clamp-on transducers.

When combining the ReVision with clampon transducers, the flow measurement becomes non-intrusive and easy from the outside of the pipe. The transducers are installed with little technical effort and without process interruption on the pipeline.

Transducer Replacement

In the unlikely event that a transducer should fail, the ReVision can be programmed to automatically compensate for the loss in path information with a little reduced accuracy in addition to advising the operator that an alarm is present. The transducer housings are separate from the transducers, allowing the transducers to be changed without special tooling and without shutting down the process. Designed to allow removal of the entire transducer for repair, replacement or cleaning without the need to dewater the pipe.


We measure everywhere.

The challenges of using natural resources are becoming ever more complex and important. In 2018, GWF Technologies GmbH was founded in Kaufbeuren, Germany, to meet these challenges. The company is able to take full advantage of the 120 years of experience of its Swiss-based parent company GWF MessSysteme AG in the fields of utility metering and data communication and can rely on a broad product and IP portfolio.

Picture: Office building in Kaufbeuren



Acoustic Flow Measurements

Our products and solutions are based on the acoustic principle of measurement ultrasound and we can draw on the wealth of experience gained from employing the technology in an array of applications. Furthermore, our products and solutions stand out due to their accuracy and reliability of measurement and the exceptional level of manufacturing quality, which is protected by proprietary IP and patents. We invest intensively in the further development of our portfolio and also overcome individual water metering challenges thanks to the competent handling of small-run and project products. Discover our products and services on the following pages. Contact us – we look forward to exchanging ideas on the key future issue of «water» and working together.


Worldwide and in various industries.

In this product overview we describe the various applications for our instruments. A vast amount of applications can be solved using acoustic flow measurement. GWF Technologies GmbH is at the forefront of «State of the Art» and future development. Our measurement instruments can be used everywhere where there is flowing water. For example rivers, channels or pipes – we measure everywhere.

Travel time system

When sound propagates through water, pressure fluctuations can be detected. They travel through the water, the channel or the pipe as sound waves. With our instruments it is possible to record these ultrasound waves.

Doppler system

Depending on the measurement technique applied, we detect the Transit Time with and against the flow direction. For other applications we use the Pulse Doppler effect. Here our instruments record the change of the wave length reflected by a particle in the flow.


Technical competence at the measuring point.

Look at him! The short target deadline was met once again. Our hard work of the past two weeks has finally paid off. The acoustic flow measuring system for a hydropower plant has passed its final test. Everything works fine − this is the best moment a project engineer can have.

Thanks to the excellent professional competence of our service department we manage projects all over the world. Skilled service technicians, electronic technicians, project engineers and training staff provide advice and support from project planning all the way to the turnkey installation. Our products are mostly customized. Prior to the project planning we inspect the measuring site in order to submit a detailed solution.

For instant clarifications you can contact our telephone support. Or browse our website on your own to find the suitable product for your application.


In operation worldwide.

We have planned, installed and commissioned installations in various countries according to customer requirements and benefits. This included the technical training of the customer.

For a list of examples, see here: Reference list

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