- Head of Department
- Department of Mathematics and Statistics
- University of Reading
- Whiteknights, PO Box 220
- Berkshire, RG6 6AX, UK

**Email address: **s.langdon@reading.ac.uk

**Telephone: **+44 (0)118 378 5021

### Boundary integral equation methods for high frequency scattering problems.

### BEM++, an open source boundary element library.

### Enhanced Acoustic Modelling for Auralisation using Hybrid Boundary Integral Methods.

### Efficient simulation of fluid flow in oil or gas reservoirs.

### Symposium of the International Association for Boundary Element Methods, June 26th-28th 2018, Paris.

### Computational Acoustics Special Interest Group, February 20th 2018, Birmingham.

### The 13th International Conference on Mathematical and Numerical Aspects of Wave Propagation, May 15th-19th 2017, Minnesota, USA.

### Wave Propagation in Complex Domains, March 30th 2017, University College London.

### The Mathematics of Finite Elements and Applications, June 14th-17th 2016, Brunel University.

### New Trends in Integral Equations, February 4th-5th 2016, Ecole Polytechnique, Paris.

### Numerical Acoustic Simulation and Auralisation as Built Environment Design Consultation Tools, September 22nd-23rd 2015, Salford.

### New Directions in Numerical Computation, August 25th-28th 2015, Oxford.

### The 12th International Conference on Mathematical and Numerical Aspects of Wave Propagation, July 20th-24th 2015, Karlsruhe, Germany.

### Boundary and Finite Element Methods for High Frequency Scattering Problems, December 15th-16th 2014, University of Reading.

### Boundary Integral Equations Analysis and Computation, May 27th-29th 2014, International Centre for Mathematical Sciences, Edinburgh.

### Scattering, Clouds and Climate workshop, March 24th-25th 2014, Oxford.

### BEM++ workshop, September 19th-20th 2013, University College London.

### The Mathematics of Finite Elements and Applications, June 11th-14th 2013, Brunel University.

### The 11th International Conference on Mathematical and Numerical Aspects of Waves, June 3rd-7th 2013, Gammarth, Tunisia.

### Association for Science Education Annual Conference, January 2nd-5th 2013, University of Reading.

### 15th IEEE International Conference on Computational Science and Engineering, December 5th-7th 2012, Paphos, Cyprus.

### Institute of Physics Tutorial Day on Numerical Modelling in Physical Acoustics, September 20th 2012, Institute of Physics, London.

### Institute of Mathematics KickOff Meeting, July 17th-18th 2012, Hamburg University of Technology.

### MATHmONDES 2012, July 9th-10th 2012, University of Reading.

### Numerical Linear Algebra, Control Theory and Data Assimilation: a conference in honour of Nancy Nichols' 70th birthday, July 2nd-3rd 2012, University of Reading.

### Eigenvalues/singular values and fast PDE algorithms: acceleration,conditioning, and stability, June 24th-29th 2012, Banff International Research Station for Mathematical Innovation and Discovery, Canada.

### Boundary Value Problems for Linear Elliptic and Integrable PDEs: Theory and Computation, May 28th-June 1st 2012, International Centre for Mathematical Sciences, Edinburgh.

### Numerical Analysis Postgraduate Seminar Day, Friday March 30th 2012, University of Reading.

- S.N. Chandler-Wilde and S. Langdon. Acoustic scattering: high frequency boundary element methods and unified transform methods, in Unified Transform for Boundary Value Problems: Applications and Advances (Fokas, Pelloni, eds.), 181-226, SIAM, Philadelphia, PA, 2015. [arxiv: 1410.6137]
- A. Gibbs, S. Langdon and A. Moiola. Numerically stable computation of embedding formulae for scattering by polygons, submitted for publication.
- S. G. Groth, D. P. Hewett and S. Langdon. A hybrid numerical-asymptotic boundary element method for high frequency scattering by penetrable convex polygons,
*Wave Motion*, 2017, doi: 10.1016/j.wavemoti.2017.12.008. - J. A. Hargreaves, Y. W. Lam and S. Langdon. A transformation approach for efficient evaluation of oscillatory surface integrals arising in three-dimensional boundary element methods,
*Int. J. Numer. Methods Engrg*, 108(2), 93-115, 2016. - T. E. Lee, M. J. Baines and S. Langdon. A finite difference moving mesh method based on conservation for moving boundary problems,
*J. Comput. Appl. Math.*, 288, 1-17, 2015. - D. P. Hewett, S. Langdon and S. N. Chandler-Wilde. A frequency-independent boundary element method for scattering by two-dimensional screens and apertures,
*IMA J. Numer. Anal.*, 35(4), 1698-1728, 2015. [arxiv: 1401.2786] - S. N. Chandler-Wilde, D. P. Hewett, S. Langdon and A. Twigger. A High Frequency Boundary Element Method for Scattering by a Class of Nonconvex Obstacles,
*Numer. Math.*, 129(4), 647-689, 2015. [arxiv: 1401.2817] - S. G. Groth, D. P. Hewett and S. Langdon. Hybrid numerical-asymptotic approximation for high frequency scattering by penetrable convex polygons,
*IMA J. Appl. Math.*, 80(2), 324-353, 2015. - T. E. Lee, M. J. Baines, S. Langdon and M. J. Tindall. A moving mesh approach for modelling avascular tumour growth.
*Appl. Numer. Math.*, 72, 99-114, 2013. - S. Langdon, D. J. Needham, B. A. Samson and J. P. Gilchrist. The unsteady flow of a weakly compressible fluid in a thin porous layer. III: Three-dimensional computations.
*Quart. J. Mech. Appl. Math.*66(1), 123-155, 2013. - D. J. Needham, S. Langdon, B. A. Samson and J. P. Gilchrist. The unsteady flow of a weakly compressible fluid in a thin porous layer. II: Three-dimensional theory.
*Quart. J. Mech. Appl. Math.*66(1), 97-122, 2013. - D. P. Hewett, S. Langdon and J. M. Melenk. A high frequency hp boundary element method for scattering by convex polygons.
*SIAM J. Numer. Anal.*, 51(1), 629-653, 2013. - S. N. Chandler-Wilde, I. G. Graham, S. Langdon and E. A. Spence. Numerical-asymptotic boundary integral methods in high frequency acoustic scattering.
*Acta Numer.*, 21, 89-305, 2012. - S. N. Chandler-Wilde, S. Langdon and M. Mokgolele. A high frequency boundary element method for scattering by convex polygons with impedance boundary conditions.
*Commun. Comput. Phys.*, 11(2), 573-593, 2012. - T. Betcke, S. N. Chandler-Wilde, I. G. Graham, S. Langdon and M. Lindner. Condition number estimates for combined potential integral operators in acoustics and their boundary element discretisation.
*Numer. Methods Partial Differential Equations*, 27(1), 31-69, 2011. [arxiv: 1007.3074] - S. Langdon, M. Mokgolele and S. N. Chandler-Wilde. High frequency scattering by convex curvilinear polygons.
*J. Comput. Appl. Math.*, 234, 2020-2026, 2010, doi: 10.1016/j.cam.2009.08.053. - S. N. Chandler-Wilde, I. G. Graham, S. Langdon and M. Lindner. Condition number estimates for combined potential boundary integral operators in acoustic scattering.
*J. Integral Equations Appl.*,**21**, 229-279, 2009. - D. J. Needham, S. Langdon, G. S. Busswell and J. P. Gilchrist. The unsteady flow of a weakly compressible fluid in a thin porous layer. I: Two-dimensional theory.
*SIAM J. Appl. Math.*,**69**, 1084-1109, 2009. - J. F. Blowey, J. R. King and S. Langdon. Small- and waiting-time behaviour of the thin-film-equation.
*SIAM J. Appl. Math.*,**67**, 1776-1807, 2007. - S. N. Chandler-Wilde and S. Langdon. A Galerkin boundary element method for high frequency scattering by convex polygons.
*SIAM J. Numer. Anal.*,**45**, 610-640, 2007. - M. Ganesh, S. Langdon and I. H. Sloan. Efficient evaluation of highly oscillatory acoustic scattering surface integrals.
*J. Comput. Appl. Math.*,**204**, 363-374, 2007. - S. Arden, S. N. Chandler-Wilde and S. Langdon. A collocation method for high frequency scattering by convex polygons.
*J. Comput. Appl. Math.*,**204**, 334-343, 2007. - S. Langdon and S. N. Chandler-Wilde. A wavenumber independent boundary element method for an acoustic scattering problem.
*SIAM J. Numer. Anal.*,**43**, 2450-2477, 2006. - S. N. Chandler-Wilde, S. Langdon and L. Ritter. A high wavenumber boundary element method for an acoustic scattering problem.
*Philos. Trans. A*,**362**, 647-671, 2004. - J. W. Barrett, S. Langdon and R. Nurnberg. Finite element approximation of a sixth order nonlinear degenerate parabolic equation.
*Numer. Math.*,**96**, 401-434, 2004. - S. Langdon and I. G. Graham. Boundary integral methods for singularly perturbed boundary value
problems.
*IMA J. Numer. Anal.***21**, 217-237, 2001 - A. Gibbs, S. Langdon and A. Moiola. Stable implementation of embedding formulae for computation of far field patterns, Proceedings of Waves 2017, Minnesota, USA, May 2017.
- J. A. Hargreaves, Y. W. Lam, S. Langdon, D. P. Hewett. A high-frequency BEM for 3D acoustic scattering, Proceedings of the 22nd International Congress on Sound and Vibration, Florence, Italy, July 2015.
- A. Gibbs, S. N. Chandler-Wilde, S. Langdon and A. Moiola. Hybrid numerical asymptotic approximation for multiple scattering problems, Proceedings of Waves 2015, Karlsruhe, Germany, July 2015.
- S. P. Groth, D. P. Hewett and S. Langdon. A high-frequency boundary element method for a transmission scattering problem, Proceedings of Waves 2015, Karlsruhe, Germany, July 2015.
- J. A. Hargreaves, D. P. Hewett, Y. W. Lam, S. Langdon. A high-frequency boundary element method for scattering by three-dimensional screens, Proceedings of Waves 2015, Karlsruhe, Germany, July 2015.
- C. Howarth, S. N. Chandler-Wilde, S. Langdon and P. Childs. Enriching a Hankel basis by ray tracing in the ultra weak variational formulation. Proceedings of Waves 2013, Gammarth, Tunisia, pp. 349-350.
- S. G. Groth, D. P. Hewett and S. Langdon. Hybrid numerical-asymptotic approximation of high frequency scattering by penetrable convex polygons. Proceedings of Waves 2013, Gammarth, Tunisia, pp. 327-328.
- S. N. Chandler-Wilde, D. P. Hewett, S. Langdon and A. Twigger. A high frequency hp-boundary element method for scattering by two-dimensional screens. Proceedings of Waves 2013, Gammarth, Tunisia, pp. 321-322.
- S. N. Chandler-Wilde, D. P. Hewett, S. Langdon and A. Twigger. A high frequency BEM for scattering by non-convex obstacles. Proc. 10th International Conference on Mathematical and Numerical Aspects of Wave Propagation, pp.307-310, 2011.
- S. Langdon and S. N. Chandler-Wilde. Boundary element methods for high frequency scattering problems. Mathematisches Forschungsinstitut Oberwolfach, Report No. 10/2010, DOI: 10.4171/OWR/2010/10, pp. 60-63, 2010.
- S. N. Chandler-Wilde, S. Langdon and A. Twigger. High frequency boundary element methods for scattering by non-convex obstacles: a model problem, pages 86-87, Proceedings of Waves 2009, the 9th International Conference on Mathematical and Numerical Aspects of Wave Propagation, 15-19 June 2009, Pau, France.
- M. Mokgolele, S. Langdon and S. N. Chandler-Wilde. High frequency scattering by a convex polygon with impedance boundary condition, pages 280-281, Proceedings of Waves 2009, the 9th International Conference on Mathematical and Numerical Aspects of Wave Propagation, 15-19 June 2009, Pau, France.
- S. N. Chandler-Wilde, S. Langdon and M. Mokgolele. Numerical methods for high frequency acoustic scattering problems. Proceedings of the Institute of Acoustics, Vol.30, pt 2, 2008.
- M. Mokgolele, S. N. Chandler-Wilde and S. Langdon. High frequency scattering by convex curvilinear polygons.
*Proc. 8th Int. Conf. on Mathematical and Numerical Aspects of Wave Propagation, Reading University*, pages 96-98, 2007. - J. M. Melenk and S. Langdon. An hp-boundary element method for high frequency scattering by convex polygons.
*Proc. 8th Int. Conf. on Mathematical and Numerical Aspects of Wave Propagation, Reading University*, pages 93-95, 2007. - S. Langdon, D. Huybrechs and S. N. Chandler-Wilde. A fully discrete collocation method for high frequency scattering by convex polygons.
*Proc. 8th Int. Conf. on Mathematical and Numerical Aspects of Wave Propagation, Reading University*, pages 84-86, 2007. - S. N. Chandler-Wilde, I. G. Graham, S. Langdon and M. Lindner. Condition Number Estimates for Combined Potential Integral Operators in Acoustic Scattering.
*Proc. 8th Int. Conf. on Mathematical and Numerical Aspects of Wave Propagation, Reading University*, pages 47-49, 2007. - S. Langdon and S. N. Chandler-Wilde. Implementation of a boundary element method for high frequency scattering by convex polygons.
*Proc. 5th U.K. Conf. on Boundary Integral Methods*, (K. Chen ed.), pages 2-11, 2005. - S. Langdon, M. Ganesh and I. H. Sloan. Approximation of high frequency acoustic wave surface integrals.
*Proc. 7th Int. Conf. on Mathematical and Numerical Aspects of Wave Propagation, Brown University, Providece, RI*, pages 157-159, 2005. - S. N. Chandler-Wilde and S. Langdon. A boundary element method for high frequency scattering by convex polygons.
*Proc. 7th Int. Conf. on Mathematical and Numerical Aspects of Wave Propagation, Brown University, Providece, RI*, pages 151-153, 2005. - S. Langdon and S. N. Chandler-Wilde. A GTD-based boundary element method for a surface scattering problem.
*Proceedings of the Institute of Acoustics***25**(5), pages 224-233, 2003. - S. Langdon and S. N. Chandler-Wilde. A Galerkin boundary element method for an acoustic scattering problem, with convergence rate independent of frequency.
*Proc. 4th U.K. Conf. on Boundary Integral Methods*, (S. Amini ed.), pages 67-76, Salford University Press 2003. - S. N. Chandler-Wilde, S. Langdon and L. Ritter. A Galerkin boundary element method for a high frequency scattering problem.
*Proc. 6th Int. Conf. on Mathematical and Numerical Aspects of Wave Propagation, University of Jyväskylä, Finland*(G. C. Cohen, E. Heikkola, P. Joly and P. Neittaanmäki, eds), pages 257-262, Springer-Verlag, Berlin 2003. - S. Langdon. A boundary integral equation method for the heat equation.
*Proc. 5th Int. Conf. on Integral Methods in Science and Engineering (IMSE98), Michigan Technological University*, (A. Struthers and B. Bertram, editors), pages 211-216.. Boca Raton FL: CRC 2000. - S. Langdon, N. Biggs, P. Chamberlain and J.-R. Li, Editorial for Waves 2007 conference, Journal of Computational and Applied Mathematics, 2009, doi: 10.1016/j.cam.2009.08.006.
- Domain Embedding Boundary Integral Equation Methods and Parabolic PDEs, Ph.D. Thesis, University of Bath, 1999.